Organic electroluminescent device emitting visible light

ABSTRACT

The invention relates to an organic electroluminescent device comprising a light-emitting layer B comprising a host material HB, a thermally activated delayed fluorescence (TADF) material EB, and a depopulation agent SB.

The present invention relates to organic electroluminescent devicescomprising a light-emitting layer B comprising a host material H^(B), athermally activated delayed fluorescence (TADF) material E^(B), and adepopulation agent S^(B).

DESCRIPTION

Organic electroluminescent devices containing one or more light-emittinglayers based on organics such as, e.g., organic light emitting diodes(OLEDs), light emitting electrochemical cells (LECs) and light-emittingtransistors gain increasing importance. In particular, OLEDs arepromising devices for electronic products such as e.g. screens, displaysand illumination devices. In contrast to most electroluminescent devicesessentially based on inorganics, organic electroluminescent devicesbased on organics are often rather flexible and producible inparticularly thin layers. The OLED-based screens and displays alreadyavailable today bear particularly beneficial brilliant colors, contrastsand are comparably efficient with respect to their energy consumption.

A central element of an organic electroluminescent device for generatinglight is a light-emitting layer placed between an anode and a cathode.When a voltage (and current) is applied to an organic electroluminescentdevice, holes and electrons are injected from an anode and a cathode,respectively, to the light-emitting layer. Typically, a hole transportlayer is located between light-emitting layer and the anode, and anelectron transport layer is located between light-emitting layer and thecathode. The different layers are sequentially disposed. Excitons ofhigh energy are then generated by recombination of the holes and theelectrons. The decay of such excited states (e.g., singlet states suchas S1 and/or triplet states such as T1) to the ground state (S0)desirably leads to light emission.

In order to enable efficient energy transport and emission, an organicelectroluminescent device comprises one or more host compounds and oneor more emitter compounds as dopants.

Challenges when generating organic electroluminescent devices are thusthe improvement of the illumination level of the devices (i.e.,brightness per current), obtaining a desired light spectrum andachieving suitable (long) lifespans.

There is still a lack of efficient and stable OLEDs that emit in thevisible light spectrum. Accordingly, there is still the unmet technicalneed for organic electroluminescent devices which have a long lifetimeand high quantum yields.

Surprisingly, it has been found that an organic electroluminescentdevice's light-emitting layer comprising one thermally activated delayedfluorescence (TADF) material, a depopulation agent and a host materialprovides an organic electroluminescent device having good lifetime andquantum yields and exhibiting emission in the visible.

Accordingly, one aspect of the present invention relates to an organicelectroluminescent device which comprises a light-emitting layer Bcomprising:

-   (i) a host material H^(B), which has a lowermost excited singlet    state energy level S1^(H), a lowermost excited triplet state energy    level T1^(H), and a highest occupied molecular orbital HOMO(H^(B))    having an energy E^(HOMO)(H^(B));-   (ii) a thermally activated delayed fluorescence (TADF) material    E^(B), which has a lowermost excited singlet state energy level    S1^(E), a lowermost excited triplet state energy level T1^(E), and a    highest occupied molecular orbital HOMO(E^(B)) having an energy    E^(HOMO)(E^(B)); and-   (iii) a depopulation agent S^(B), which has a lowermost excited    singlet state energy level S1^(S), optionally a lowermost excited    triplet state energy level T1^(S), and a highest occupied molecular    orbital HOMO(S^(B)) having an energy E^(HOMO)(S^(B));    wherein E^(B) emits thermally activated delayed fluorescence;    and wherein the relations expressed by the following formulas (1)    to (3) and either (4a) and (4b), or (5a) and (5b) apply:

S1^(H) >S1^(E)  (1)

S1^(H) >S1^(S)  (2)

S1>S1^(E)  (3)

E ^(HOMO)(E ^(B))≥E ^(HOMO)(H ^(B))  (4a)

0.2 eV≥E ^(HOMO)(S ^(B))−E ^(HOMO)(E ^(B))≥0.8 eV  (4b)

E ^(HOMO)(H ^(B))≥E ^(HOMO)(E ^(B))  (5a)

0.2 eV≥E ^(HOMO)(S ^(B))−E ^(HOMO)(H ^(B))≥0.8 eV  (5b).

According to the invention, the lowermost excited singlet state of thehost material H^(B) is higher in energy than the lowermost excitedsinglet state of the thermally activated delayed fluorescence (TADF)material E^(B).

The lowermost excited singlet state of the host material H^(B) is higherin energy than the lowermost excited singlet state of the depopulationagent S^(B). The lowermost excited singlet state of the TADF materialE^(B) is lower in energy than the lowermost excited singlet state of thedepopulation agent S^(B).

In one aspect of the invention, the highest occupied molecular orbitalof the TADF material E^(B) (E^(HOMO)(E^(B))) is higher in energy thanthe highest occupied molecular orbital of the host material H^(B)(E^(HOMO)(H^(B))) (i.e. the TADF material E^(B) acts as the main holetransport material). In this aspect, the highest occupied molecularorbital of the depopulation agent S^(B) (E^(HOMO)(S^(B))) is higher inenergy than the highest occupied molecular orbital of the TADF materialE^(B) (E^(HOMO)(E^(B))). Preferably, the energy difference betweenE^(HOMO)(S^(B))−E^(HOMO)(E^(B)) is at least 0.2 eV and not more than 0.8eV, in particular at least 0.25 eV and not more than 0.55 eV.

In an alternative aspect of the invention, the highest occupiedmolecular orbital of the host material H^(B) (E^(HOMO)(H^(B))) is higherin energy than the highest occupied molecular orbital of the TADFmaterial E^(B) (E^(HOMO)(E^(B))) (i.e. the host material H^(B) acts asthe main hole transport material). In this aspect, the highest occupiedmolecular orbital of the depopulation agent S^(B) (E^(HOMO)(S^(B))) ishigher in energy than the highest occupied molecular orbital of the hostmaterial H^(B) (E^(HOMO)(H^(B))) Preferably, the energy differencebetween E^(HOMO)(S^(B))−E^(HOMO)(H^(B)) is at least 0.2 eV and not morethan 0.8 eV, in particular at least 0.25 eV and not more than 0.55 eV.Preferably, the energy difference betweenE^(HOMO)(S^(B))−E^(HOMO)(E^(B)) is at least 0.15 eV, at least 0.16 eV,at least 0.17 eV, at least 0.18 eV, at least 0.19 eV, at least 0.20 eV,at least 0.21 eV, at least 0.22 eV, at least 0.23 eV, at least 0.24 eV,or at least 0.25 eV. Preferably, the energy difference betweenE^(HOMO)(S^(B))−E^(HOMO)(E^(B)) is not more than 0.8 eV, not more than0.75 eV, not more than 0.70 eV, not more than 0.65 eV, not more than0.60 eV, or not more than 0.55 eV.

In an alternative aspect of the invention, the highest occupiedmolecular orbital of the host material H^(B) is equal in energy than thehighest occupied molecular orbital of the TADF material E^(B). In thisaspect, the highest occupied molecular orbital of the depopulation agentS^(B) (E^(HOMO)(S^(B))) is higher in energy than the highest occupiedmolecular orbital of the host material H^(B) (E^(HOMO)(H^(B))) and/orthe highest occupied molecular orbital of the TADF material E^(B)(E^(HOMO)(E^(B))). Preferably, the energy difference betweenE^(HOMO)(S^(B))−E^(HOMO)(H^(B)) and/or the energy difference betweenE^(HOMO)(S^(B))−E^(HOMO)(E^(B)) is at least 0.2 eV and not more than 0.8eV, in particular at least 0.25 eV and not more than 0.55 eV.Preferably, the energy difference betweenE^(HOMO)(S^(B))−E^(HOMO)(H^(B)) is at least 0.15 eV, at least 0.16 eV,at least 0.17 eV, at least 0.18 eV, at least 0.19 eV, at least 0.20 eV,at least 0.21 eV, at least 0.22 eV, at least 0.23 eV, at least 0.24 eV,or at least 0.25 eV. Preferably, the energy difference betweenE^(HOMO)(S^(B))−E^(HOMO)(H^(B)) is not more than 0.8 eV, not more than0.75 eV, not more than 0.70 eV, not more than 0.65 eV, not more than0.60 eV, or not more than 0.55 eV.

As used herein, the terms “TADF material” and “TADF emitter” and “TADFemitters” may be understood interchangeably. When one of the terms“emitter” “emitter compound” or the like is used, this may be understoodin that preferably a TADF material of the present invention is meant, inparticular one or those designated as E^(B).

According to the present invention, a TADF material is characterized inthat it exhibits a ΔE_(ST) value, which corresponds to the energydifference between the lowermost excited singlet state (S1) and thelowermost excited triplet state (T1), of less than 0.4 eV, preferablyless than 0.3 eV, more preferably less than 0.2 eV.

Accordingly in an embodiment of the present invention, the TADF materialE^(B) is characterized in that it has a ΔE_(ST) value, which correspondsto the energy difference between S1^(E) and T1^(E), of less than 0.4 eV.In a preferred embodiment of the present invention, the TADF materialE^(B) is characterized in that it has a ΔE_(ST) value of less than 0.3eV, less than 0.2 eV.

In a preferred embodiment, the lowermost excited triplet state of thehost material H^(B) (T1^(H)) is higher in energy than the lowermostexcited triplet state of the TADF material E^(B) (T^(E)): T1^(H)>T1^(E).

In one embodiment of the invention, mass ratio of TADF material E^(B) tothe depopulation agent S^(B) (E^(B) S^(B)) is >1. In one embodiment ofthe invention, the mass ratio E^(B):S^(B) is in the range of from 1.5:1to 30:1, in the range of from 2:1 to 25:1, or in the range of from 3:1to 20:1. For example, the mass ratio E^(B):S^(B) is in the range of(approximately) 20:1, 15:1, 12:1, 10:1, 8:1, 5:1, or 4:1.

As used herein, the terms organic electroluminescent device andopto-electronic light-emitting devices may be understood in the broadestsense as any device comprising a light-emitting layer B comprising ahost material H^(B), a TADF material E^(B) and a depopulation agentS^(B).

It will be understood that the light-emitting layer B may also comprisemore than one TADF materials E^(B) and/or more than one depopulationagent S^(B) each having the properties as described herein. According tothe present invention, the light-emitting layer B comprises at least oneTADF material E^(B) and at least one depopulation agent S^(B) eachhaving the properties as described herein. According to one embodimentof the present invention, the light-emitting layer B comprises one TADFmaterial E^(B) and one depopulation agent S^(B) each having theproperties as described herein.

As used herein, the terms organic electroluminescent device andopto-electronic light-emitting devices may be understood in the broadestsense as any device comprising a light-emitting layer B comprising ahost material H^(B), a TADF material E^(B) and a depopulation agentS^(B).

The organic electroluminescent device may be understood in the broadestsense as any device based on organic materials that is suitable foremitting light in the visible or nearest ultraviolet (UV) range, i.e.,in the range of a wavelength of from 380 to 800 nm. More preferably,organic electroluminescent device may be able to emit light in thevisible range, i.e., of from 400 to 800 nm.

In a preferred embodiment, the organic electroluminescent device is adevice selected from the group consisting of an organic light emittingdiode (OLED), a light emitting electrochemical cell (LEC), and alight-emitting transistor.

Particularly preferably, the organic electroluminescent device is anorganic light emitting diode (OLED). Optionally, the organicelectroluminescent device as a whole may be intransparent,semi-transparent or (essentially) transparent.

The term “layer” as used in the context of the present inventionpreferably is a body that bears an extensively planar geometry. Thelight-emitting layer B preferably bears a thickness of not more than 1mm, more preferably not more than 0.1 mm, even more preferably not morethan 10 μm, even more preferably not more than 1 μm, in particular notmore than 0.1 μm.

The person skilled in the art will notice that the light-emitting layerB will typically be incorporated in the organic electroluminescentdevice of the present invention. Preferably, such organicelectroluminescent device comprises at least the following layers: atleast one light-emitting layer B, at least one anode layer A and atleast one cathode layer C.

Preferably, the anode layer A contains at least one component selectedfrom the group consisting of indium tin oxide, indium zinc oxide, PbO,SnO, graphite, doped silicium, doped germanium, doped GaAs, dopedpolyaniline, doped polypyrrole, doped polythiophene, and mixtures of twoor more thereof.

Preferably, the cathode layer C contains at least one component selectedfrom the group consisting of Al, Au, Ag, Pt, Cu, Zn, Ni, Fe, Pb, In, W,Pd, LiF, Ca, Ba, Mg, and mixtures or alloys of two or more thereof.

Preferably, the light-emitting layer B is located between an anode layerA and a cathode layer C. Accordingly, the general set-up is preferablyA-B-C. This does of course not exclude the presence of one or moreoptional further layers. These can be present at each side of A, of Band/or of C.

In a preferred embodiment, the organic electroluminescent devicecomprises at least the following layers:

-   A) an anode layer A containing at least one component selected from    the group consisting of indium tin oxide, indium zinc oxide, PbO,    SnO, graphite, doped silicium, doped germanium, doped GaAs, doped    polyaniline, doped polypyrrole, doped polythiophene, and mixtures of    two or more thereof;-   B) the light-emitting layer B; and-   C) a cathode layer C containing at least one component selected from    the group consisting of Al, Au, Ag, Pt, Cu, Zn, Ni, Fe, Pb, In, W,    Pd, LiF, Ca, Ba, Mg, and mixtures or alloys of two or more thereof,    wherein the light-emitting layer B is located between the anode    layer A and the a cathode layer C.

In one embodiment, when the organic electroluminescent device is anOLED, it may optionally comprise the following layer structure:

A) an anode layer A, exemplarily comprising indium tin oxide (ITO); HTL)a hole transport layer HTL;B) a light-emitting layer B according to present invention as describedherein; ETL) an electron transport layer ETL; andC) a cathode layer, exemplarily comprising Al, Ca and/or Mg.

Preferably, the order of the layers herein is A-HTL-B-ETL-C.

Furthermore, the organic electroluminescent device may optionallycomprise one or more protective layers protecting the device fromdamaging exposure to harmful species in the environment including,exemplarily moisture, vapor and/or gases.

Preferably, the anode layer A is located on the surface of a substrate.The substrate may be formed by any material or composition of materials.Most frequently, glass slides are used as substrates. Alternatively,thin metal layers (e.g., copper, gold, silver or aluminum films) orplastic films or slides may be used. This may allow a higher degree offlexibility. The anode layer A is mostly composed of materials allowingto obtain an (essentially) transparent film. As at least one of bothelectrodes should be (essentially) transparent in order to allow lightemission from the OLED, either the anode layer A or the cathode layer Ctransparent. Preferably, the anode layer A comprises a large content oreven consists of transparent conductive oxides (TCOs).

Such anode layer A may exemplarily comprise indium tin oxide, aluminumzinc oxide, fluor tin oxide, indium zinc oxide, PbO, SnO, zirconiumoxide, molybdenum oxide, vanadium oxide, wolfram oxide, graphite, dopedSi, doped Ge, doped GaAs, doped polyaniline, doped polypyrrol and/ordoped polythiophene.

Particularly preferably, the anode layer A (essentially) consists ofindium tin oxide (ITO) (e.g., (InO₃)_(0.9)(SnO₂)_(0.1)). The roughnessof the anode layer A caused by the transparent conductive oxides (TCOs)may be compensated by using a hole injection layer (HIL). Further, theHIL may facilitate the injection of quasi charge carriers (i.e., holes)in that the transport of the quasi charge carriers from the TCO to thehole transport layer (HTL) is facilitated. The hole injection layer(HIL) may comprise poly-3,4-ethylendioxy thiophene (PEDOT), polystyrenesulfonate (PSS), MoO₂, V₂O₅, CuPC or CuI, in particular a mixture ofPEDOT and PSS. The hole injection layer (HIL) may also prevent thediffusion of metals from the anode layer A into the hole transport layer(HTL). The HIL may exemplarily comprise PEDOT:PSS (poly-3,4-ethylendioxythiophene:polystyrene sulfonate), PEDOT (poly-3,4-ethylendioxythiophene), mMTDATA (4,4′,4″-tris[phenyl(m-tolyl)amino]triphenylamine),Spiro-TAD (2,2′,7,7′-tetrakis(n,n-diphenylamino)-9,9′-spirobifluorene),DNTPD(N1,N1′-(biphenyl-4,4′-diyl)bis(N1-phenyl-N4,N4-di-m-tolylbenzene-1,4-diamine),NPB(N,N′-nis-(1-naphthalenyl)-N,N′-bis-phenyl-(1,1′-biphenyl)-4,4′-diamine),NPNPB (N,N′-diphenyl-N,N′-di-[4-(N,N-diphenyl-amino)-phenyl]benzidine),MeO-TPD (N,N,N′,N′-tetrakis(4-methoxyphenyl)-benzi-dine), HAT-CN(1,4,5,8,9,11-hexaazatriphenylen-hexacarbonitrile) and/or Spiro-NPD(N,N′-diphenyl-N,N′-bis-(1-naphthyl)-9,9′-spirobifluorene-2,7-diamine).

Adjacent to the anode layer A or hole injection layer (HIL) typically ahole transport layer (HTL) is located. Herein, any hole transportcompound may be used. Exemplarily, electron-rich heteroaromaticcompounds such as triarylamines and/or carbazoles may be used as holetransport compound. The HTL may decrease the energy barrier between theanode layer A and the light-emitting layer B (serving as emitting layer(EML)). The hole transport layer (HTL) may also be an electron blockinglayer (EBL). Preferably, hole transport compounds bear comparably highenergy levels of their triplet states T1. Exemplarily the hole transportlayer (HTL) may comprise a star-shaped heterocycle such astris(4-carbazoyl-9-ylphenyl)amine (TCTA), poly-TPD(poly(4-butylphenyl-diphenyl-amine)), [alpha]-NPD(poly(4-butylphenyl-diphenyl-amine)), TAPC(4,4′-cyclohexyliden-bis[N,N-bis(4-methylphenyl)benzenamine]), 2-TNATA(4,4′,4″-tris[2-naphthyl(phenyl)-amino]triphenylamine), Spiro-TAD,DNTPD, NPB, NPNPB, MeO-TPD, HAT-CN and/or TrisPcz(9,9′-diphenyl-6-(9-phenyl-9H-carbazol-3-yl)-9H,9′H-3,3′-bicarbazole).In addition, the HTL may comprise a p-doped layer, which may be composedof an inorganic or organic dopant in an organic hole-transportingmatrix. Transition metal oxides such as vanadium oxide, molybdenum oxideor tungsten oxide may exemplarily be used as inorganic dopant.

Tetrafluorotetracyanoquinodimethane (F4-TCNQ),copper-pentafluorobenzoate (Cu(I)pFBz) or transition metal complexes mayexemplarily be used as organic dopant.

The EBL may exemplarily comprise mCP (1,3-bis(carbazol-9-yl)benzene),TCTA, 2-TNATA, mCBP (3,3-di(9H-carbazol-9-yl)biphenyl),9-[3-(dibenzofuran-2-yl)phenyl]-9H-carbazole,9-[3-(dibenzofuran-2-yl)phenyl]-9H-carbazole,9-[3-(dibenzothiophen-2-yl)phenyl]-9H-carbazole,9-[3,5-bis(2-dibenzofuranyl)phenyl]-9H-carbazole,9-[3,5-bis(2-dibenzothiophenyl)phenyl]-9H-carbazole, tris-Pcz, CzSi(9-(4-tert-butylphenyl)-3,6-bis(triphenylsilyl)-9H-carbazole), and/orDCB (N,N′-dicarbazolyl-1,4-dimethylbenzene).

In one embodiment of the invention, the depopulation agent S^(B) isselected from the group consisting of a fluorescence emitter and anorganic TADF emitter, whereas the organic TADF emitter is characterizedin that it has a ΔE_(ST) value, which corresponds to the energydifference between S1^(S) and T1^(S), of less than 0.4 eV.

In a preferred embodiment, the depopulation agent S^(B) is an organicTADF emitter or a combination of two or more organic TADF emitters. In apreferred embodiment, the depopulation agent S^(B) is an organic TADFemitter.

In another embodiment of the invention, the relation expressed byformula (6a), (6b) or (6c) applies:

E ^(HOMO)(E ^(B))>E ^(HOMO)(H ^(B))  (6a)

E ^(HOMO)(H ^(B))>E ^(HOMO)(E ^(B))  (6b)

−0.2 eV≤E ^(HOMO)(H ^(B))−E ^(HOMO)(E ^(B))≤0.2 eV  (6c).

In another embodiment of the invention, the relation between the lowestunoccupied molecular orbital LUMO(E^(B)) of the TADF material E^(B)having an energy E^(LUMO)(E^(B)) and the lowest unoccupied molecularorbital LUMO(S^(B)) of the depopulation agent S^(B) having an energyE^(LUMO)(S^(B)) expressed by formula (7) applies:

E ^(LUMO)(S ^(B))>E ^(LUMO)(E ^(B))  (7)

In one embodiment of the invention, the relation expressed by formulas(8) applies:

0.2 eV≤E ^(LUMO)(S ^(B))−E ^(LUMO)(E ^(B))≤0.8 eV  (8a).

In one embodiment of the present invention, the depopulation agent S^(B)is a TADF material, i.e., one or more TADF emitter. Accordingly in anembodiment of the present invention, the depopulation agent S^(B) ischaracterized in that it has a ΔE_(ST) value, which corresponds to theenergy difference between S1^(S) and T1^(S), of less than 0.4 eV. In apreferred embodiment of the present invention, the depopulation agentS^(B) is characterized in that it has a ΔE_(ST) value of less than 0.3eV, less than 0.2 eV, less than 0.1 eV, or even less than 0.05 eV.

In one embodiment of the present invention, the TADF material E^(B) andthe depopulation agent S^(B) are both organic TADF emitters.

In one embodiment of the invention, the lowermost excited triplet stateenergy level T1^(E) of the TADF material E^(B) is between 2.2 eV and 3.5eV, preferably between 2.3 eV and 3.2 eV, more preferably between 2.4 eVand 3.1 eV or even between 2.5 eV and 3.0 eV.

According to the invention, the emission layer B comprises at least onehost material H^(B), the TADF material E^(B) and the depopulation agentS^(B).

In a preferred embodiment of the invention, the light-emitting layer Bcomprises 39.8-98%, more preferably 57-93%, even more preferably 74-87%by weight of the host compound H^(B).

In a preferred embodiment of the invention, the light-emitting layer Bcomprises 0.1-50%, more preferably 0.5-40%, even more preferably 1-30%by weight of the TADF material E^(B).

In a preferred embodiment of the invention, the light-emitting layer Bcomprises 0.1-10%, more preferably 0.5-8%, even more preferably 1-5% byweight of the depopulation agent S^(B).

In a preferred embodiment of the invention, the TADF material E^(B) isan organic TADF emitter or a combination of two or more organic TADFemitters

In a preferred embodiment of the invention, the depopulation agent S^(B)is an organic TADF emitter, wherein the light-emitting layer B comprises0.1-10%, more preferably 0.5-8%, even more preferably 1-5% by weight ofthe depopulation agent S^(B).

In a preferred embodiment of the invention, the depopulation agent S^(B)is a NRCT emitter, wherein the light-emitting layer B comprises 0.1-10%,more preferably 0.5-8%, even more preferably 1-5% by weight of thedepopulation agent S^(B).

In one embodiment of the invention, the depopulation agent S^(B) is afluorescence emitter, wherein the light-emitting layer B comprises0.1-10%, more preferably 0.5-8%, even more preferably 1-5% by weight ofthe depopulation agent S^(B).

In a preferred embodiment of the invention, the TADF material E^(B) isan organic TADF emitter, wherein the light-emitting layer B comprises1-50%, more preferably 5-40%, even more preferably 10-30% by weight ofthe TADF material E^(B).

In a preferred embodiment of the invention, the TADF material E^(B) is aNRCT emitter, wherein the light-emitting layer B comprises 0.1-10%, morepreferably 0.5-5%, even more preferably 1-3% by weight of the TADFmaterial E^(B).

In a preferred embodiment of the invention, the light-emitting layer Bcomprises up to 93% by weight of one or more further host compoundsH^(B2) differing from H^(B).

In a preferred embodiment of the invention, the light-emitting layer Bcomprises up to 93% by weight of one or more solvents.

In a preferred embodiment of the invention, the light-emitting layer Bcomprises (or consists of):

-   (i) 39.8-98%, more preferably 57-93%, even more preferably 74-87% by    weight of the host compound H^(B);-   (ii) 0.1-50%, more preferably 0.5-40%, even more preferably 1-30% by    weight of the TADF material E^(B); and-   (iii) 0.1-50%, more preferably 0.5-40%, even more preferably 1-30%    by weight of the depopulation agent S^(B); and optionally-   (iv) 0-60% by weight of one or more further host compounds H^(B2)    differing from H^(B); and optionally-   (v) 0-60% by weight of one or more solvents; and optionally-   (vi) 0-30% by weight of at least one further emitter molecule F.

Preferably, the contents of (i) to (v) sum up to 100% by weight.

In a preferred embodiment, the depopulation agent S^(B) and the TADFmaterial E^(B) are each independently from each other a NRCT emitter,wherein the light-emitting layer B comprises (or consists of):

-   (i) 39.8-98%, more preferably 57-93%, even more preferably 74-87% by    weight of the host compound H^(B);-   (ii) 0.1-10%, more preferably 0.5-5%, even more preferably 1-3% by    weight of the TADF material E^(B); and-   (iii) 0.1-10%, more preferably 0.5-5%, even more preferably 1-3% by    weight of the depopulation agent S^(B); and optionally-   (iv) 0-60% by weight of one or more further host compounds H^(B2)    differing from H^(B); and optionally-   (v) 0-60% by weight of one or more solvents; and optionally-   (vi) 0-30% by weight of at least one further emitter molecule F.

In a preferred embodiment, the depopulation agent S^(B) is an organicTADF emitter and the TADF material E^(B) is a NRCT emitter, wherein thelight-emitting layer B comprises (or consists of):

-   (i) 39.8-98%, more preferably 57-93%, even more preferably 74-87% by    weight of the host compound H^(B);-   (ii) 0.1-10%, more preferably 0.5-5%, even more preferably 1-3% by    weight of the TADF material E^(B); and-   (iii) 1-50%, more preferably 5-40%, even more preferably 10-30% by    weight of the depopulation agent S^(B); and optionally-   (iv) 0-59.9% by weight of one or more further host compounds H^(B2)    differing from H^(B); and optionally-   (v) 0-59.9% by weight of one or more solvents; and optionally-   (vi) 0-30% by weight of at least one further emitter molecule F.

In a preferred embodiment, the depopulation agent S^(B) is a NRCTemitter and the TADF material E^(B) is an organic TADF emitter, whereinthe light-emitting layer B comprises (or consists of):

-   (i) 39.8-98%, more preferably 57-93%, even more preferably 74-87% by    weight of the host compound H^(B);-   (ii) 1-50%, more preferably 5-40%, even more preferably 10-30% by    weight of the TADF material E^(B); and-   (iii) 0.1-10%, more preferably 0.5-5%, even more preferably 1-3% by    weight of the depopulation agent S^(B); and optionally-   (iv) 0-59.1% by weight of one or more further host compounds H^(B2)    differing from H^(B); and optionally-   (v) 0-59.1% by weight of one or more solvents; and optionally-   (vi) 0-30% by weight of at least one further emitter molecule F.

In a preferred embodiment, the depopulation agent S^(B) is afluorescence emitter and the TADF material E^(B) is a NRCT emitter,wherein the light-emitting layer B comprises (or consists of):

-   (i) 39.8-98%, more preferably 57-93%, even more preferably 74-87% by    weight of the host compound H^(B);-   (ii) 0.1-10%, more preferably 0.5-5%, even more preferably 1-3% by    weight of the TADF material E^(B); and-   (iii) 0.1-10%, more preferably 0.5-5%, even more preferably 1-3% by    weight of the depopulation agent S^(B); and optionally-   (iv) 0-60% by weight of one or more further host compounds H^(B2)    differing from H^(B); and optionally-   (v) 0-60% by weight of one or more solvents; and optionally-   (vi) 0-30% by weight of at least one further emitter molecule F.

In a preferred embodiment, the depopulation agent S^(B) is afluorescence emitter and the TADF material E^(B) is an organic TADFemitter, wherein the light-emitting layer B comprises (or consists of):

-   (i) 39.8-98%, more preferably 57-93%, even more preferably 74-87% by    weight of the host compound H^(B);-   (ii) 1-50%, more preferably 5-40%, even more preferably 10-30% by    weight of the TADF material E^(B); and-   (iii) 0.1-10%, more preferably 0.5-5%, even more preferably 1-3% by    weight of the depopulation agent S^(B); and optionally-   (iv) 0-59.1% by weight of one or more further host compounds H^(B2)    differing from H^(B); and optionally-   (v) 0-59.1% by weight of one or more solvents; and optionally-   (vi) 0-30% by weight of at least one further emitter molecule F.

Exemplarily, the host material H^(B) and/or the optionally presentfurther host compound H^(B2) may be selected from the group consistingof CBP (4,4′-Bis-(N-carbazolyl)-biphenyl), mCP, mCBP Sif87(dibenzo[b,d]thiophen-2-yltriphenylsilane), CzSi, Sif88(dibenzo[b,d]thiophen-2-yl)diphenylsilane), DPEPO(bis[2-(diphenylphosphino)phenyl] ether oxide),9-[3-(dibenzofuran-2-yl)phenyl]-9H-carbazole,9-[3-(dibenzofuran-2-yl)phenyl]-9H-carbazole,9-[3-(dibenzothiophen-2-yl)phenyl]-9H-carbazole,9-[3,5-bis(2-dibenzofuranyl)phenyl]-9H-carbazole,9-[3,5-bis(2-dibenzothiophenyl)phenyl]-9H-carbazole, T2T(2,4,6-tris(biphenyl-3-yl)-1,3,5-triazine), T3T(2,4,6-tris(triphenyl-3-yl)-1,3,5-triazine) and/or TST(2,4,6-tris(9,9′-spirobifluorene-2-yl)-1,3,5-triazine). In oneembodiment of the invention, the emission layer B comprises a so-calledmixed-host system with at least one hole-dominant (n-type) host and oneelectron-dominant (p-type) host.

In one embodiment, the emission layer B comprises the TADF materialE^(B) and the depopulation agent S^(B) (which is exemplarily a secondTADF material S^(B)), and hole-dominant host H^(B) selected from thegroup consisting of CBP, mCP, mCBP,9-[3-(dibenzofuran-2-yl)phenyl]-9H-carbazole,9-[3-(dibenzofuran-2-yl)phenyl]-9H-carbazole,9-[3-(dibenzothiophen-2-yl)phenyl]-9H-carbazole,9-[3,5-bis(2-dibenzofuranyl)phenyl]-9H-carbazole and9-[3,5-bis(2-dibenzothiophenyl)phenyl]-9H-carbazole.

As used herein, if not defined more specifically in a particularcontext, the designation of the colors of emitted and/or absorbed lightis as follows:

violet: wavelength range of >380-420 nm;deep blue: wavelength range of >420-470 nm;sky blue: wavelength range of >470-500 nm;green: wavelength range of >500-560 nm;yellow: wavelength range of >560-580 nm;orange: wavelength range of >580-620 nm;red: wavelength range of >620-800 nm.

With respect to emitter compounds, such colors refer to the emissionmaximum λmax^(PMMA) of a poly(methyl methacrylate) (PMMA) film withtypically 1-10% by weight of the emitter. Therefore, exemplarily, a deepblue emitter has an emission maximum λmax^(PMMA) in the range of from420 to 470 nm, a sky blue emitter has an emission maximum λmax_(PMMA) inthe range of from 470 to 500 nm, a green emitter has an emission maximumλmax_(PMMA) in a range of from 500 to 560 nm, a red emitter has anemission maximum λmax_(PMMA) in a range of from 620 to 800 nm.

In one embodiment of the invention, the organic electroluminescentdevice exhibits green emission.

In one embodiment of the invention, the organic electroluminescentdevice exhibits blue emission.

In one embodiment of the invention, the organic electroluminescentdevice exhibits red emission.

In a preferred embodiment of the invention, the organicelectroluminescent device exhibits an emission maximum k_(max)(D) of 440to 560 nm.

In a preferred embodiment of the invention, the organicelectroluminescent device exhibits an emission maximum k_(max)(D) of 440to 470 nm.

In a preferred embodiment of the invention, the organicelectroluminescent device exhibits an emission maximum k_(max)(D) of 510to 550 nm.

Near-Range-Charge-Transfer (NRCT) Emitters

A Near-range-charge-transfer (NRCT) emitter in the context of thepresent invention is any emitter that has an emission spectrum, whichexhibits a full width at half maximum (FWHM) of less than or equal to0.25 eV (s 0.25 eV), measured with 1% by weight of NRCT emitter in PMMAat room temperature (RT).

As used herein and not otherwise specified, the each spectral propertydetermined herein is determined at a content of 1% by weight of therespective emitter in PMMA at room temperature (RT). As used herein andnot otherwise specified, the FWHM is determined at a content of 1% byweight of the respective emitter in PMMA at room temperature (RT).

In a preferred embodiment of the present invention, a NRCT emitter inthe context of the present invention is any emitter that has an emissionspectrum, which exhibits a FWHM of ≤0.24 eV, more preferably ≤0.23 eV,even more preferably ≤0.22 eV, ≤0.21 eV or ≤0.20 eV, measured with 1% byweight of NRCT emitter in PMMA at room temperature (RT). In otherembodiments of the present invention, an emitter exhibits a FWHM of≤0.19 eV, ≤0.19 eV, ≤0.18 eV, ≤0.17 eV, ≤0.16 eV, ≤0.15 eV, ≤0.14 eV,≤0.13 eV, ≤0.12 eV, or ≤0.11 eV.

Typical NRCT emitters are described in literature by Hatakeyama et al.(Advanced Materials, 2016, 28(14):2777-2781, DOI:10.1002/adma.201505491) to show a delayed component in the time-resolvedphotoluminescence spectrum and exhibits a near-range HOMO-LUMOseparation as described. The emitters shown in Hatakeyama et al. may beNRCT emitters, which are also TADF emitters in the sense of the presentinvention.

Typical NRCT emitters only show one emission band in the emissionspectrum, wherein typical fluorescence emitters display several distinctemission bands due to vibrational progression.

In one embodiment of the invention, the TADF material E^(B) and/or thedepopulation agent S^(B) is a NRCT emitter. In one embodiment of theinvention, the TADF material E^(B) and the depopulation agent S^(B) areboth each a NRCT emitter. In another embodiment of the invention, theTADF material E^(B) is no NRCT emitter. In this case, the TADF materialE^(B) is an emitter which shows TADF properties, but not the propertiesof a NRCT emitter as defined herein. In further embodiment of theinvention, the depopulation agent S^(B) is no NRCT emitter. In thiscase, the depopulation agent S^(B) is an emitter which does not have theproperties of a NRCT emitter as defined herein. In one embodiment of theinvention, the depopulation agent S^(B) is a fluorescent emitter. In oneembodiment of the invention, the depopulation agent S^(B) is afluorescent emitter which is no NRCT emitter. In further embodiment ofthe invention, neither the TADF material E^(B) nor the depopulationagent S^(B) are NRCT emitters.

An NRCT emitter may, in each context of the present invention,optionally each be a boron containing NRCT emitter, in particular a blueboron containing NRCT emitter.

In a preferred embodiment, the TADF material E^(B) is a NRCT emitter.

In one embodiment, the TADF material E^(B) and/or the depopulation agentS^(B) is a boron containing NRCT emitter.

In one embodiment, the TADF material E^(B) and the depopulation agentS^(B) is a boron containing NRCT emitter.

In a preferred embodiment, the TADF material E^(B) is a boron containingNRCT emitter.

In one embodiment, the TADF material E^(B) is a blue boron containingNRCT emitter.

In a preferred embodiment, a NRCT emitter comprises or consists of apolycyclic aromatic compound.

TADF material E^(B) and/or the depopulation agent S^(B) comprises orconsists of a polycyclic aromatic compound.

In a preferred embodiment, the emission spectrum of a film with 1% byweight of the TADF material E^(B) has a full width at half maximum(FWHM), which is smaller than 0.2 eV.

In a preferred embodiment, the TADF material E^(B) is a boron containingemitter with an emission spectrum of a film with 1% by weight of theTADF material E^(B), which has a full width at half maximum (FWHM),which is smaller than 0.2 eV.

In a preferred embodiment, the TADF material E^(B) is a blue boroncontaining emitter with an emission spectrum of a film with 1% by weightof the TADF material E^(B), which has a full width at half maximum(FWHM), which is smaller than 0.2 eV.

In a preferred embodiment, the TADF material E^(B) comprises or consistsof a polycyclic aromatic compound with an emission spectrum of a filmwith 1% by weight of the TADF material E^(B), which has a full width athalf maximum (FWHM), which is smaller than 0.2 eV.

In a preferred embodiment, the TADF material E^(B) comprises or consistsof a polycyclic aromatic compound according to formula (1) or (2) or aspecific example described in US-A 2015/236274. US-A 2015/236274 alsodescribes examples for synthesis of such compounds.

In one embodiment, the TADF material E^(B) comprises or consists of astructure according to Formula I:

Wherein n is 0 or 1.

m=1−n.

X¹ is N or B. X² is N or B. X³ is N or B.

W is selected from the group consisting of Si(R³)₂, C(R³)₂ and BR³.each of R¹, R² and R³ is independently from each other selected from thegroup consisting of:C₁-C₅-alkyl, which is optionally substituted with one or moresubstituents R⁶;C₆-C₆₀-aryl, which is optionally substituted with one or moresubstituents R⁶; andC₃-C₅₇-heteroaryl, which is optionally substituted with one or moresubstituents R⁶;each of R^(I), R^(II), R^(III), R^(IV), R^(V), R^(VI), R^(VII),R^(VIII), R^(IX), R^(X), and R^(XI) is independently from anotherselected from the group consisting of: hydrogen, deuterium, N(R⁵)₂, OR⁵,Si(R⁵)₃, B(OR⁵)₂, OSO₂R⁵, CF₃, CN, halogen,C₁-C₄₀-alkyl, which is optionally substituted with one or moresubstituents R⁵ and wherein one or more non-adjacent CH₂-groups are eachoptionally substituted by R⁵C═CR⁵, C≡C, Si(R⁵)₂, Ge(R⁵)₂, Sn(R⁵)₂, C═O,C═S, C═Se, C═NR⁵, P(═O)(R⁵), SO, SO₂, NR⁵, O, S or CONR⁵;C₁-C₄₀-alkoxy, which is optionally substituted with one or moresubstituents R⁵ and wherein one or more non-adjacent CH₂-groups are eachoptionally substituted by R⁵C═CR⁵, C≡C, Si(R⁵)₂, Ge(R⁵)₂, Sn(R⁵)₂, C═O,C═S, C═Se, C═NR⁵, P(═O)(R⁵), SO, SO₂, NR⁵, O, S or CONR⁵;C₁-C₄₀-thioalkoxy, which is optionally substituted with one or moresubstituents R⁵ and wherein one or more non-adjacent CH₂-groups are eachoptionally substituted by R⁵C═CR⁵, C≡C, Si(R⁵)₂, Ge(R⁵)₂, Sn(R⁵)₂, C═O,C═S, C═Se, C═NR⁵, P(═O)(R⁵), SO, SO₂, NR⁵, O, S or CONR⁵;C₂-C₄₀-alkenyl, which is optionally substituted with one or moresubstituents R⁵ and wherein one or more non-adjacent CH₂-groups are eachoptionally substituted by R⁵C═CR⁵, C≡C, Si(R⁵)₂, Ge(R⁵)₂, Sn(R⁵)₂, C═O,C═S, C═Se, C═NR⁵, P(═O)(R⁵), SO, SO₂, NR⁵, O, S or CONR⁵;C₂-C₄₀-alkynyl, which is optionally substituted with one or moresubstituents R⁵ and wherein one or more non-adjacent CH₂-groups are eachoptionally substituted by R⁵C═CR⁵, C≡C, Si(R⁵)₂, Ge(R⁵)₂, Sn(R⁵)₂, C═O,C═S, C═Se, C═NR⁵, P(═O)(R⁵), SO, SO₂, NR⁵, O, S or CONR⁵;C₆-C₆₀-aryl, which is optionally substituted with one or moresubstituents R⁵; andC₃-C₅₇-heteroaryl, which is optionally substituted with one or moresubstituents R⁵.R⁵ is at each occurrence independently from another selected from thegroup consisting of: hydrogen, deuterium, OPh, CF₃, CN, F,C₁-C₅-alkyl, wherein optionally one or more hydrogen atoms areindependently from each other substituted by deuterium, CN, CF₃, or F;C₁-C₅-alkoxy, wherein optionally one or more hydrogen atoms areindependently from each other substituted by deuterium, CN, CF₃, or F;C₁-C₅-thioalkoxy, wherein optionally one or more hydrogen atoms areindependently from each other substituted by deuterium, CN, CF₃, or F;C₂-C₅-alkenyl, wherein optionally one or more hydrogen atoms areindependently from each other substituted by deuterium, CN, CF₃, or F;C₂-C₅-alkynyl, wherein optionally one or more hydrogen atoms areindependently from each other substituted by deuterium, CN, CF₃, or F;C₆-C₁₈-aryl, which is optionally substituted with one or moreC₁-C₅-alkyl substituents;C₃-C₁₇-heteroaryl, which is optionally substituted with one or moreC₁-C₅-alkyl substituents;N(C₆-C₁₈-aryl)₂,N(C₃-C₁₇-heteroaryl)₂; andN(C₃-C₁₇-heteroaryl)(C₆-C₁₈-aryl).R⁶ is at each occurrence independently from another selected from thegroup consisting of hydrogen, deuterium, OPh, CF₃, CN, F,C₁-C₅-alkyl, wherein optionally one or more hydrogen atoms areindependently from each other substituted by deuterium, CN, CF₃, or F;C₁-C₅-alkoxy, wherein optionally one or more hydrogen atoms areindependently from each other substituted by deuterium, CN, CF₃, or F;C₁-C₅-thioalkoxy, wherein optionally one or more hydrogen atoms areindependently from each other substituted by deuterium, CN, CF₃, or F;C₂-C₅-alkenyl, wherein optionally one or more hydrogen atoms areindependently from each other substituted by deuterium, CN, CF₃, or F;C₂-C₅-alkynyl, wherein optionally one or more hydrogen atoms areindependently from each other substituted by deuterium, CN, CF₃, or F;C₆-C₁₈-aryl, which is optionally substituted with one or moreC₁-C₅-alkyl substituents;C₃-C₁₇-heteroaryl, which is optionally substituted with one or moreC₁-C₅-alkyl substituents;N(C₆-C₁₈-aryl)₂;N(C₃-C₁₇-heteroaryl)₂; andN(C₃-C₁₇-heteroaryl)(C₆-C₁₈-aryl).

According to a preferred embodiment, two or more of the substituentsselected from the group consisting of R^(I), R^(II), R^(III), R^(IV),R^(V), R^(VI), R^(VII), R^(VIII), R^(IX), R^(X), and R^(XI) that arepositioned adjacent to another may each form a mono- or polycyclic,aliphatic, aromatic and/or benzo-fused ring system with another.

According to a preferred embodiment, at least one of X¹, X² and X³ is Band at least one of X¹, X² and X³ is N.

According to a preferred embodiment of the invention, at least onesubstituent selected from the group consisting of R^(I), R^(II),R^(III), R_(IV), R^(V), R^(VI), R^(VII), R^(VIII), R^(IX), R^(X), andR^(XI) optionally forms a mono- or polycyclic, aliphatic, aromaticand/or benzo-fused ring system with one or more substituents of the samegroup that is/are positioned adjacent to the at least one substituent.

According to a preferred embodiment of the invention, at least one ofX¹, X² and X³ is B and at least one of X¹, X² and X³ is N.

In one embodiment, the TADF material E^(B) comprises or consists of astructure according to Formula 1 and n=0.

In one embodiment, each of R¹ and R² is each independently from eachother selected from the group consisting of

C₁-C₅-alkyl, which is optionally substituted with one or moresubstituents R⁶;C₆-C₃₀-aryl, which is optionally substituted with one or moresubstituents R⁶; andC₃-C₃₀-heteroaryl, which is optionally substituted with one or moresubstituents R⁶.

In one embodiment, R¹ and R² is each independently from each otherselected from the group consisting of Me, ^(i)Pr, ^(t)Bu, CN, CF₃,

Ph, which is optionally substituted with one or more substituentsindependently from each other selected from the group consisting of Me,^(i)Pr, ^(t)Bu, CN, CF₃, and Ph;

-   pyridinyl, which is optionally substituted with one or more    substituents independently from each other selected from the group    consisting of Me, ^(i)Pr, ^(t)Bu, CN, CF₃, and Ph;-   pyrimidinyl, which is optionally substituted with one or more    substituents independently from each other selected from the group    consisting of Me, ^(i)Pr, ^(t)Bu, CN, CF₃, and Ph; and-   triazinyl, which is optionally substituted with one or more    substituents independently from each other selected from the group    consisting of Me, ^(i)Pr, ^(t)Bu, CN, CF₃, and Ph.

In one embodiment, each of R^(I), R^(II), R^(III), R^(IV), R^(V),R^(VI), R^(VII), R^(VIII), R^(IX), R^(X), and R^(XI) is independentlyfrom another selected from the group consisting of: hydrogen, deuterium,halogen, Me, ^(i)Pr, ^(t)Bu, CN, CF₃,

-   Ph, which is optionally substituted with one or more substituents    independently from each other selected from the group consisting of    Me, ^(i)Pr, ^(t)Bu, CN, CF₃, and Ph:-   pyridinyl, which is optionally substituted with one or more    substituents independently from each other selected from the group    consisting of Me, ^(i)Pr, ^(t)Bu, CN, CF₃, and Ph;-   pyrimidinyl, which is optionally substituted with one or more    substituents independently from each other selected from the group    consisting of Me, ^(i)Pr, ^(t)Bu, CN, CF₃, and Ph;-   carbazolyl, which is optionally substituted with one or more    substituents independently from each other selected from the group    consisting of Me, ^(i)Pr, ^(t)Bu, CN, CF₃, and Ph;-   triazinyl, which is optionally substituted with one or more    substituents independently from each other selected from the group    consisting of Me, ^(i)Pr, ^(t)Bu, CN, CF₃, and Ph;-   and N(Ph)₂.

In one embodiment, each of R^(I), R^(II), R^(III), R^(IV), R^(V),R^(VI), R^(VII), R^(VIII), R^(IX), R^(X), and R^(XI) is independentlyfrom another selected from the group consisting of: hydrogen, deuterium,halogen, Me, ^(i)Pr, ^(t)Bu, CN, CF₃,

-   Ph, which is optionally substituted with one or more substituents    independently from each other selected from the group consisting of    Me, ^(i)Pr, ^(t)Bu, CN, CF₃, and Ph;-   pyridinyl, which is optionally substituted with one or more    substituents independently from each other selected from the group    consisting of Me, ^(i)Pr, ^(t)Bu, CN, CF₃, and Ph;-   pyrimidinyl, which is optionally substituted with one or more    substituents independently from each other selected from the group    consisting of Me, ^(i)Pr, ^(t)Bu, CN, CF₃, and Ph;-   carbazolyl, which is optionally substituted with one or more    substituents independently from each other selected from the group    consisting of Me, ^(i)Pr, ^(t)Bu, CN, CF₃, and Ph;-   triazinyl, which is optionally substituted with one or more    substituents independently from each other selected from the group    consisting of Me, ^(i)Pr, ^(t)Bu, CN, CF₃, and Ph;-   and N(Ph)₂; and    R¹ and R² is each independently from each other selected from the    group consisting of    C₁-C₅-alkyl, which is optionally substituted with one or more    substituents R⁶;    C₆-C₃n-aryl, which is optionally substituted with one or more    substituents R⁶; and    C₃-C₃₀-heteroaryl, which is optionally substituted with one or more    substituents R⁶.

In one embodiment of the invention, the depopulation agent S^(B) is anear-range-charge-transfer (NRCT) emitter. According to the invention, aNRCT material shows a delayed component in the time-resolvedphotoluminescence spectrum and exhibits a near-range HOMO-LUMOseparation as described by Hatakeyama et al. (Advanced Materials, 2016,28(14):2777-2781, DOI: 10.1002/adma.201505491).

In one embodiment, the depopulation agent S^(B) is a boron containingNRCT emitter.

In one embodiment, the depopulation agent S^(B) is a blue boroncontaining NRCT emitter.

In a preferred embodiment, the depopulation agent S^(B) comprises orconsists of a polycyclic aromatic compound.

In a preferred embodiment, the emission spectrum of a film with 1% byweight of the depopulation agent S^(B) has a full width at half maximum(FWHM), which is smaller than 0.2 eV.

In a preferred embodiment, the depopulation agent S^(B) is a boroncontaining emitter with an emission spectrum of a film with 1% by weightof the depopulation agent S^(B), which has a full width at half maximum(FWHM), which is smaller than 0.2 eV.

In a preferred embodiment, the depopulation agent S^(B) is a blue boroncontaining emitter with an emission spectrum of a film with 1% by weightof the depopulation agent S^(B), which has a full width at half maximum(FWHM), which is smaller than 0.2 eV.

In a preferred embodiment, the depopulation agent S^(B) comprises orconsists of a polycyclic aromatic compound with an emission spectrum ofa film with 1% by weight of, the depopulation agent S^(B), which has afull width at half maximum (FWHM), which is smaller than 0.2 eV.

In a preferred embodiment, the depopulation agent S^(B) comprises orconsists of a polycyclic aromatic compound according to formula (1) or(2) or a specific example described in US-A 2015/236274. US-A2015/236274 also describes examples for synthesis of such compounds.

In one embodiment, the depopulation agent S^(B) comprises or consists ofa structure according to Formula I.

In a one embodiment, the TADF material E^(B) and/or the depopulationagent S^(B) is a blue boron-containing NRCT emitter selected from thefollowing group:

In a one embodiment, the TADF material E^(B) and/or the depopulationagent S^(B) is a green boron-containing NRCT emitter selected from thefollowing group:

Organic TADF Emitters

In a preferred embodiment, the TADF material E^(B) and/or thedepopulation agent S^(B) is an organic TADF material. According to theinvention, organic emitter or organic material means that the emitter ormaterial (predominantly) consists of the elements hydrogen (H), carbon(C), nitrogen (N), boron (B), silicon (Si) and optionally fluorine (F),optionally bromine (Br) and optionally oxygen (O). Particularlypreferably, it does not contain any transition metals.

In a preferred embodiment, the TADF material E^(B) is an organic TADFmaterial. In a preferred embodiment, the depopulation agent S^(B) is anorganic emitter. In a more preferred embodiment, the TADF material E^(B)and the depopulation agent S^(B) are both organic TADF materials.

In a preferred embodiment, the TADF material E^(B) and/or thedepopulation agent S^(B) is an organic TADF material, which is chosenfrom molecules of a structure of Formula I-TADF

-   -   wherein    -   is at each occurrence independently from another 1 or 2;    -   p is at each occurrence independently from another 1 or 2;    -   X is at each occurrence independently from another selected        Ar^(EWG), H, CN or CF₃;    -   Z is at each occurrence independently from another selected from        the group consisting of a direct bond, CR³R⁴, C═CR³R⁴, C═O,        C═NR³, NR³, O, SiR³R⁴, S, S(O) and S(O)₂;    -   Ar^(EWG) is at each occurrence independently from another a        structure according to one of Formulas IIa to IIk

wherein # represents the binding site of the single bond linkingAr^(EWG) to the substituted central phenyl ring of Formula I-TADF;R¹ is at each occurrence independently from another selected from thegroup consisting of hydrogen, deuterium, C₁-C₅-alkyl, wherein one ormore hydrogen atoms are optionally substituted by deuterium, andC₆-C₁₈-aryl, which is optionally substituted with one or moresubstituents R⁶;R² is at each occurrence independently from another selected from thegroup consisting of hydrogen, deuterium, C₁-C₅-alkyl, wherein one ormore hydrogen atoms are optionally substituted by deuterium, andC₆-C₁₈-aryl, which is optionally substituted with one or moresubstituents R⁶;R^(a), R³ and R⁴ is at each occurrence independently from anotherselected from the group consisting of hydrogen, deuterium, N(R⁵)₂, OR⁵,SR⁵, Si(R⁵)₃, CF₃, CN, F,C₁-C₄₀-alkyl which is optionally substituted with one or moresubstituents R⁵ and wherein one or more non-adjacent CH₂-groups areoptionally substituted by R⁵C═CR⁵, C≡C, Si(R⁵)₂, Ge(R⁵)₂, Sn(R⁵)₂, C═O,C═S, C═Se, C═NR⁵, P(═O)(R⁵), SO, SO₂, NR⁵, O, S or CONR⁵;C₁-C₄₀-thioalkoxy which is optionally substituted with one or moresubstituents R⁵ and wherein one or more non-adjacent CH₂-groups areoptionally substituted by R⁵C═CR⁵, C≡C, Si(R⁵)₂, Ge(R⁵)₂, Sn(R⁵)₂, C═O,C═S, C═Se, C═NR⁵, P(═O)(R⁵), SO, SO₂, NR⁵, O, S or CONR⁵; andC₆-C₆₀-aryl which is optionally substituted with one or moresubstituents R⁵; C₃-C₅₇-heteroaryl which is optionally substituted withone or more substituents R⁵;R⁵ is at each occurrence independently from another selected from thegroup consisting of hydrogen, deuterium, N(R⁶)₂, OR⁶, SR⁶, Si(R⁶)₃, CF₃,CN, F, C₁-C₄₀-alkyl which is optionally substituted with one or moresubstituents R⁶ and wherein one or more non-adjacent CH₂-groups areoptionally substituted by R⁶C═CR⁶, C≡C, Si(R⁶)₂, Ge(R⁶)₂, Sn(R⁶)₂, C═O,C═S, C═Se, C═NR⁶, P(═O)(R⁶), SO, SO₂, NR⁶, O, S or CONR⁶;C₆-C₆₀-aryl which is optionally substituted with one or moresubstituents R⁶; and C₃-C₅₇-heteroaryl which is optionally substitutedwith one or more substituents R⁶;R⁶ is at each occurrence independently from another selected from thegroup consisting of hydrogen, deuterium, OPh, CF₃, CN, F,C₁-C₅-alkyl, wherein one or more hydrogen atoms are optionally,independently from each other substituted by deuterium, CN, CF₃, or F;C₁-C₅-alkoxy,wherein one or more hydrogen atoms are optionally, independently fromeach other substituted by deuterium, CN, CF₃, or F;C₁-C₅-thioalkoxy, wherein one or more hydrogen atoms are optionally,independently from each other substituted by deuterium, CN, CF₃, or F;C₆-C₁₈-aryl which is optionally substituted with one or more C₁-C₅-alkylsubstituents;C₃-C₁₇-heteroaryl which is optionally substituted with one or moreC₆-C₁₈-aryl substituents and/or one or more C₁-C₅-alkyl substituents;N(C₆-C₁₈-aryl)₂;N(C₃-C₁₇-heteroaryl)₂, andN(C₃-C₁₇-heteroaryl)(C₆-C₁₈-aryl);R^(d) is at each occurrence independently from another selected from thegroup consisting of hydrogen, deuterium, N(R⁵)₂, OR⁵,SR⁵, Si(R⁵)₃, CF₃, CN, F,C₁-C₄₀-alkyl which is optionally substituted with one or moresubstituents R⁵ and wherein one or more non-adjacent CH₂-groups areoptionally substituted by R⁵C═CR⁵, C≡C, Si(R⁵)₂, Ge(R⁵)₂, Sn(R⁵)₂, C═O,C═S, C═Se, C═NR⁵, P(═O)(R⁵), SO, SO₂, NR⁵, O, S or CONR⁵;C₁-C₄₀-thioalkoxy which is optionally substituted with one or moresubstituents R⁵ and wherein one or more non-adjacent CH₂-groups areoptionally substituted by R⁵C═CR⁵, C≡C, Si(R⁵)₂, Ge(R⁵)₂, Sn(R⁵)₂, C═O,C═S, C═Se, C═NR⁵, P(═O)(R⁵), SO, SO₂, NR⁵, O, S or CONR⁵; andC₆-C₆₀-aryl which is optionally substituted with one or moresubstituents R⁵; C₃-C₅₇-heteroaryl which is optionally substituted withone or more substituents R⁵;wherein the substituents R^(a), R³, R⁴ or R⁵ independently from eachother optionally may form a mono- or polycyclic, aliphatic, aromaticand/or benzo-fused ring system with one or more other substituentsR^(a), R³, R⁴ or R⁵ andwherein the one or more substituents R^(d) independently from each otheroptionally may form a mono- or polycyclic, aliphatic, aromatic and/orbenzo-fused ring system with one or more other substituents R^(d).

According to the invention, the substituents R^(a), R³, R⁴ or R⁵ at eachoccurrence independently from each other may optionally form a mono- orpolycyclic, aliphatic, aromatic and/or benzo-fused ring system with oneor more other substituents R^(a), R³, R⁴ or R⁵.

According to the invention, the substituents R^(d) at each occurrenceindependently from each other may optionally form a mono- or polycyclic,aliphatic, aromatic and/or benzo-fused ring system with one or moreother substituents R^(d).

In a particularly preferred embodiment of the invention, Z is a directbond at each occurrence.

In a preferred embodiment, the TADF material E^(B) is an organic TADFmaterial, which is chosen from molecules of a structure of FormulaI-TADF.

In one embodiment of the invention, the TADF material E^(B) comprises atleast one triazine structure according to Formula IIa.

In a preferred embodiment, the TADF material E^(B) is an organic TADFmaterial, which is chosen from molecules of a structure of FormulaII-TADF

In one embodiment of the invention, R^(a) is at each occurrenceindependently from another selected from the group consisting ofhydrogen, deuterium, Me, ^(i)Pr, ^(t)Bu, CN, CF₃,

Ph, which is optionally substituted with one or more substituentsindependently from each other selected from the group consisting of Me,^(i)Pr, ^(t)Bu, CN, CF₃ and Ph;pyridinyl, which is optionally substituted with one or more substituentsindependently from each other selected from the group consisting of Me,^(i)Pr, ^(t)Bu, CN, CF₃ and Ph;pyrimidinyl, which is optionally substituted with one or moresubstituents independently from each other selected from the groupconsisting of Me, ^(i)Pr, ^(t)Bu, CN, CF₃ and Ph;carbazolyl, which is optionally substituted with one or moresubstituents independently from each other selected from the groupconsisting of Me, ^(i)Pr, ^(t)Bu, CN, CF₃ and Ph;triazinyl, which is optionally substituted with one or more substituentsindependently from each other selected from the group consisting of Me,^(i)Pr, ^(t)Bu, CN, CF₃ and Ph; and N(Ph)₂.

In one embodiment of the invention, R^(d) is at each occurrenceindependently from another selected from the group consisting ofhydrogen, deuterium, Me, ^(i)Pr, ^(t)Bu, CN, CF₃,

Ph, which is optionally substituted with one or more substituentsindependently from each other selected from the group consisting of Me,^(i)Pr, ^(t)Bu, CN, CF₃ and Ph;pyridinyl, which is optionally substituted with one or more substituentsindependently from each other selected from the group consisting of Me,^(i)Pr, ^(t)Bu, CN, CF₃ and Ph;pyrimidinyl, which is optionally substituted with one or moresubstituents independently from each other selected from the groupconsisting of Me, ^(i)Pr, ^(t)Bu, CN, CF₃ and Ph;carbazolyl, which is optionally substituted with one or moresubstituents independently from each other selected from the groupconsisting of Me, ^(i)Pr, ^(t)Bu, CN, CF₃ and Ph;triazinyl, which is optionally substituted with one or more substituentsindependently from each other selected from the group consisting of Me,^(i)Pr, ^(t)Bu, CN, CF₃ and Ph; and N(Ph)₂.

In a preferred embodiment, X is CN.

In one embodiment of the invention, the TADF material E^(B) is chosenfrom a structure of Formula III:

wherein R^(a), X and R¹ are defined as above.

In one embodiment of the invention, E^(B) is chosen from molecules of astructure of Formula IIIa:

wherein R^(a), X and R¹ are defined as above.

In one embodiment of the invention, E^(B) is chosen from molecules of astructure of Formula IIIa-1:

wherein R^(a), X and R¹ are defined as above.

In one embodiment of the invention, E^(B) is chosen from molecules of astructure of Formula IIIa-2:

wherein R^(a), X and R¹ are defined as above.

In one embodiment of the invention, E^(B) is chosen from molecules of astructure of Formula IIIb:

wherein R^(a) and R¹ are defined as above.

In one embodiment of the invention, E^(B) is chosen from molecules of astructure of Formula IIIa-1:

wherein R^(a) and R¹ are defined as above.

In one embodiment of the invention, E^(B) is chosen from molecules of astructure of Formula IIIc:

wherein R^(a) and R¹ are defined as above.

In one embodiment of the invention, E^(B) is chosen from molecules of astructure of Formula IIId:

wherein R^(a) and R¹ are defined as above.

In one embodiment of the invention, E^(B) is chosen from molecules of astructure of Formula IV:

wherein R^(a), R¹ and X are defined as above.

In one embodiment of the invention, E^(B) is chosen from molecules of astructure of Formula IVa:

wherein R^(a), R¹ and X are defined as above.

In one embodiment of the invention, E^(B) is chosen from molecules of astructure of Formula IVb:

wherein R^(a) and R¹ are defined as above.

In one embodiment of the invention, E^(B) is chosen from molecules of astructure of Formula V:

wherein R^(a), R¹ and X are defined as above.

In one embodiment of the invention, E^(B) is chosen from molecules of astructure of Formula Va:

wherein R^(a), R¹ and X are defined as above.

In one embodiment of the invention, E^(B) is chosen from molecules of astructure of Formula Vb:

wherein R^(a) and R¹ are defined as above.

In one embodiment of the invention, E^(B) is chosen from molecules of astructure of Formula VI:

wherein R^(a), R¹ and X are defined as above.

In one embodiment of the invention, E^(B) is chosen from molecules of astructure of Formula Via:

wherein R^(a), R¹ and X are defined as above.

In one embodiment of the invention, E^(B) is chosen from molecules of astructure of Formula VIb:

wherein R^(a) and R¹ are defined as above.

In one embodiment of the invention, E^(B) is chosen from molecules of astructure of Formula VII:

wherein R^(a) and X are defined as above.

In one embodiment of the invention, E^(B) is chosen from molecules of astructure of Formula VIIa:

wherein R^(a) and X are defined as above.

In one embodiment of the invention, E^(B) is chosen from molecules of astructure of Formula VIIb:

wherein R^(a) is defined as above.

In one embodiment of the invention, E^(B) is chosen from molecules of astructure of Formula VIII:

wherein R^(a) and X are defined as above.

In one embodiment of the invention, E^(B) is chosen from molecules of astructure of Formula VIIIa:

wherein R^(a) and X are defined as above.

In one embodiment of the invention, E^(B) is chosen from molecules of astructure of Formula VIIIb:

wherein R^(a) is defined as above.

In one embodiment of the invention, E^(B) is chosen from molecules of astructure of Formula IX:

wherein R^(a) and X are defined as above.

In one embodiment of the invention, E^(B) is chosen from molecules of astructure of Formula IXa:

wherein R^(a) and X are defined as above.

In one embodiment of the invention, E^(B) is chosen from molecules of astructure of Formula IXb:

wherein R^(a) is defined as above.

In one embodiment of the invention, E^(B) is chosen from molecules of astructure of Formula X:

wherein R^(a) and X are defined as above.

In one embodiment of the invention, E^(B) is chosen from molecules of astructure of Formula Xa:

wherein R^(a) and X are defined as above.

In one embodiment of the invention, E^(B) is chosen from molecules of astructure of Formula Xb:

wherein R^(a) is defined a s above.

In one embodiment of the invention, E^(B) is chosen from molecules of astructure of Formula XI:

wherein R^(a) and X are defined as above.

In one embodiment of the invention, E^(B) is chosen from molecules of astructure of Formula XIa:

wherein R^(a) and X are defined as above.

In one embodiment of the invention, E^(B) is chosen from molecules of astructure of Formula XIb:

wherein R^(a) is defined as above.

In one embodiment of the invention, E^(B) is chosen from molecules of astructure of Formula XII:

wherein R^(a), X and R^(d) are defined as above.

In one embodiment of the invention, E^(B) is chosen from molecules of astructure of Formula XIIa:

wherein R^(a), X and R^(d) are defined as above.

In one embodiment of the invention, E^(B) is chosen from molecules of astructure of Formula XIIb:

wherein R^(a), X and R^(d) are defined as above.

The synthesis of the molecules of a structure of Formula I-TADF can beaccomplished via standard reactions and reaction conditions known to theskilled artesian. Typically, in a first step a coupling reaction,preferably a palladium catalyzed coupling reaction, is performed.

E1 can be any boronic acid (R^(B)=H) or an equivalent boronic acid ester(R^(B)=alkyl or aryl), in particular two R^(B) form a ring to give e.g.boronic acid pinacol esters, of fluoro-(trifluoromethyl)phenyl,difluoro-(trifluoromethyl)phenyl, fluoro-(cyano)phenyl ordifluoro-(cyano)phenyl. As second reactant E2 preferably Ar^(E)WG-Br isused. Reaction conditions of such palladium catalyzed coupling reactionsare known the person skilled in the art, e.g. from WO 2017/005699, andit is known that the reacting groups of E1 and E2 can be interchanged tooptimize the reaction yields.

In a second step, the molecules according to Formula I-TADF are obtainedvia the reaction of a nitrogen heterocycle in a nucleophilic aromaticsubstitution with the aryl halide, preferably aryl fluoride, or aryldihalide, preferably aryl difluoride, E3. Typical conditions include theuse of a base, such as tribasic potassium phosphate or sodium hydride,for example, in an aprotic polar solvent, such as dimethyl sulfoxide(DMSO) or N,N-dimethylformamide (DMF), for example.

In particular, the donor molecule E6 is a 3,6-substituted carbazole(e.g., 3,6-dimethylcarbazole, 3,6 diphenylcarbazole,3,6-di-tert-butylcarbazole), a 2,7-substituted carbazole (e.g., 2,7dimethylcarbazole, 2,7-diphenylcarbazole, 2,7-di-tert-butylcarbazole), a1,8-substituted carbazole (e.g., 1,8-dimethylcarbazole,1,8-diphenylcarbazole, 1,8-di-tert-butylcarbazole), a 1 substitutedcarbazole (e.g., 1-methylcarbazole, 1-phenylcarbazole,1-tert-butylcarbazole), a 2 substituted carbazole (e.g.,2-methylcarbazole, 2-phenylcarbazole, 2-tert-butylcarbazole), or a 3substituted carbazole (e.g., 3-methylcarbazole, 3-phenylcarbazole,3-tert-butylcarbazole).

Alternatively, a halogen-substituted carbazole, particularly3-bromocarbazole, can be used as E6.

In a subsequent reaction a boronic acid ester functional group orboronic acid functional group may be exemplarily introduced at theposition of the one or more halogen substituents, which was introducedvia E6, to yield the corresponding carbazol-3-ylboronic acid ester orcarbazol-3-ylboronic acid, e.g., via the reaction withbis(pinacolato)diboron (CAS No. 73183-34-3). Subsequently, one or moresubstituents R^(a) may be introduced in place of the boronic acid estergroup or the boronic acid group via a coupling reaction with thecorresponding halogenated reactant R^(a)-Hal, preferably R^(a)—Cl andR^(a)—Br.

Alternatively, one or more substituents R^(a) may be introduced at theposition of the one or more halogen substituents, which was introducedvia D-H, via the reaction with a boronic acid of the substituent R^(a)[R^(a)—B(OH)₂] or a corresponding boronic acid ester.

An alternative synthesis route comprises the introduction of a nitrogenheterocycle via copper- or palladium-catalyzed coupling to an arylhalide or aryl pseudohalide, preferably an aryl bromide, an aryl iodide,aryl triflate or an aryl tosylate.

Device wherein the depopulation agent S^(B) is a blue fluorescenceemitter

In one embodiment of the invention, the depopulation agent S^(B) is afluorescence emitter, in particular a blue fluorescence emitter.

In one embodiment, the depopulation agent S^(B) is a blue fluorescenceemitter selected from the following group:

In certain embodiments, the depopulation agent S^(B) is a bluefluorescence emitter selected from the following group:

Device Wherein the Depopulation Agent S^(B) is a Triplet-TripletAnnihilation (TTA) Fluorescence Emitter

In one embodiment of the invention, the depopulation agent S^(B) is atriplet-triplet annihilation (TTA) emitter.

In one embodiment, S^(B) is a blue TTA emitter selected from thefollowing group:

Device Wherein the Depopulation Agent S^(B) is a Green FluorescenceEmitter

In a further embodiment of the invention, the depopulation agent S^(B)is a fluorescence emitter, in particular a green fluorescence emitter.

In one embodiment, the depopulation agent S^(B) is a fluorescenceemitter selected from the following group:

In a further embodiment of the invention, the device has an emissionpeak in the visible or nearest ultraviolet range, i.e., in the range ofa wavelength of from 380 to 800 nm, in particular between 485 nm and 590nm, preferably between 505 nm and 565 nm, even more preferably between515 nm and 545 nm.

Device Wherein the Depopulation Agent S^(B) is a Red FluorescenceEmitter

In a further embodiment of the invention, the depopulation agent S^(B)is a fluorescence emitter, in particular a red fluorescence emitter.

In one embodiment, the depopulation agent S^(B) is a fluorescenceemitter selected from the following group:

In one embodiment, the depopulation agent S^(B) is a phosphorescenceemitter.

In a further embodiment of the invention, the device has an emissionpeak in the visible or nearest ultraviolet range, i.e., in the range ofa wavelength of from 380 to 800 nm, in particular between 590 nm and 690nm, preferably between 610 nm and 665 nm, even more preferably between620 nm and 640 nm.

Orbital and excited state energies can be determined either by means ofexperimental methods known to the person skilled in the art.Experimentally, the energy of the highest occupied molecular orbitalE^(HOMO) is determined by methods known to the person skilled in the artfrom cyclic voltammetry measurements with an accuracy of 0.1 eV. Theenergy of the lowest unoccupied molecular orbital E^(LUMO) is calculatedas E^(HOMO)+E^(gap), where E^(gap) is determined as follows:

For host compounds, the onset of emission of a film with 10% by weightof host in poly(methyl methacrylate) (PMMA) is used as E^(gap), unlessstated otherwise.

For emitter compounds, e.g., NRCT emitters and fluorescence emitters,E^(gap) is determined as the energy at which the excitation and emissionspectra of a film with 1% by weight of emitter in PMMA cross, unlessstated otherwise.

For organic TADF emitters, E^(gap) is determined as the energy at whichthe excitation and emission spectra of a film with 10% by weight ofemitter in PMMA cross, unless stated otherwise.

For host compounds, the onset of emission of a film with 10% by weightof host in poly(methyl methacrylate) (PMMA), which corresponds to theenergy of the first excited singlet state S1, is used as E^(gap), unlessstated otherwise.

For emitter compounds, e.g., NRCT emitters and fluorescence emitters,E^(gap) and thus the energy of the first excited singlet state S1 isdetermined in the same way, unless stated otherwise.

For organic TADF emitters, the onset of emission of a film with 10% byweight of host in poly(methyl methacrylate) (PMMA), which corresponds tothe energy of the first excited singlet state S1, is used as E^(gap),unless stated otherwise.

For host compounds, the energy of the first excited triplet state T1 isdetermined from the onset of the time-gated emission spectrum at 77 K,typically with a delay time of 1 ms and an integration time of 1 ms, ifnot otherwise stated measured in a film of poly(methyl methacrylate)(PMMA) with 10% by weight of host.

For emitter compounds, e.g., NRCT emitters and fluorescence emitters,the energy of the first excited triplet state T1 is determined from theonset of the time-gated emission spectrum at 77 K, typically with adelay time of 1 ms and an integration time of 1 ms, if not otherwisestated measured in a film of poly(methyl methacrylate) (PMMA) with 1% byweight of emitter.

For organic TADF emitters, the energy of the first excited triplet stateT1 is determined from the onset of the time-gated emission spectrum at77 K, typically with a delay time of 1 ms and an integration time of 1ms, if not otherwise stated measured in a film of poly(methylmethacrylate) (PMMA) with 10% by weight of TADF compound.

For TADF compounds, the energy of the first excited triplet state T1 isdetermined from the onset of the time-gated emission spectrum at 77 K,typically with a delay time of 1 ms and an integration time of 1 ms.

In the electron transport layer (ETL, any electron transporter may beused. Exemplarily, compounds poor of electrons such as, e.g.,benzimidazoles, pyridines, triazoles, oxadiazoles (e.g.,1,3,4-oxadiazole), phosphinoxides and sulfone, may be used. Exemplarily,an electron transporter ETM^(D) may also be a star-shaped heterocyclesuch as 1,3,5-tri(1-phenyl-1H-benzo[d]imidazol-2-yl)phenyl (TPBi). TheETM^(D) may exemplarily be NBphen(2,9-bis(naphthalen-2-yl)-4,7-diphenyl-1, 10-phenanthroline), Alq3(Aluminum-tris(8-hydroxyquinoline)), TSPO1(diphenyl-4-triphenylsilylphenyl-phosphinoxide), BPyTP2(2,7-di(2,2′-bipyridin-5-yl)triphenyle), Sif87(dibenzo[b,d]thiophen-2-yltriphenylsilane), Sif88(dibenzo[b,d]thiophen-2-yl)diphenylsilane), BmPyPhB(1,3-bis[3,5-di(pyridin-3-yl)phenyl]benzene) and/or BTB(4,4′-bis-[2-(4,6-diphenyl-1,3,5-triazinyl)]-1,1′-biphenyl). Optionally,the electron transport layer may be doped with materials such as Liq(8-hydroxyquinolinolatolithium). Optionally, a second electron transportlayer may be located between electron transport layer and the cathodelayer C.

Adjacent to the electron transport layer (ETL), a cathode layer C may belocated. Exemplarily, the cathode layer C may comprise or may consist ofa metal (e.g., Al, Au, Ag, Pt, Cu, Zn, Ni, Fe, Pb, LiF, Ca, Ba, Mg, In,W, or Pd) or a metal alloy. For practical reasons, the cathode layer Cmay also consist of (essentially) intransparent metals such as Mg, Ca orAl. Alternatively or additionally, the cathode layer C may also comprisegraphite and or carbon nanotubes (CNTs). Alternatively, the cathodelayer C may also consist of nanoscale silver wires.

An OLED may further, optionally, comprise a protection layer between theelectron transport layer (ETL) D and the cathode layer C (which may bedesignated as electron injection layer (EIL)). This layer may compriselithium fluoride, caesium fluoride, silver, Liq(8-hydroxyquinolinolatolithium), Li₂O, BaF₂, MgO and/or NaF.

Accordingly, a further embodiment of the present invention relates to anOLED, which exhibits an external quantum efficiency at 1000 cd/m² ofmore than 10%, more preferably of more than 12%, more preferably of morethan 15%, even more preferably of more than 17% or even more than 20%and/or exhibits an emission maximum between 490 nm and 570 nm,preferably between 500 nm and 560 nm, more preferably between 510 nm and550 nm, even more preferably between 520 nm and 540 nm and/or exhibits aLT80 value at 500 cd/m² of more than 3000 h, preferably more than 6000h, more preferably more than 12000 h, even more preferably more than22500 h or even more than 30000 h.

Accordingly, a further embodiment of the present invention relates to anOLED, which exhibits an external quantum efficiency at 1000 cd/m² ofmore than 10%, more preferably of more than 12%, more preferably of morethan 15%, even more preferably of more than 17% or even more than 20%and/or exhibits an emission maximum between 420 nm and 500 nm,preferably between 430 nm and 490 nm, more preferably between 440 nm and480 nm, even more preferably between 450 nm and 470 nm and/or exhibits aLT80 value at 500 cd/m² of more than 100 h, preferably more than 200 h,more preferably more than 400 h, even more preferably more than 750 h oreven more than 1000 h.

A further embodiment of the present invention relates to an OLED, whichemits light at a distinct color point. According to the presentinvention, the OLED emits light with a narrow emission band (small fullwidth at half maximum (FWHM)). In a preferred embodiment, the OLEDaccording to the invention emits light with a FWHM of the main emissionpeak of below 0.43 eV, more preferably of below 0.39 eV, even morepreferably of below 0.35 eV or even below 0.31 eV.

In a particularly preferred embodiment, the depopulation agent S^(B) isa NRCT emitter and the OLED according to the invention emits light witha FWHM of the main emission peak of below 0.25 eV, more preferably ofbelow 0.23 eV, even more preferably of below 0.21 eV or even below 0.20eV.

A further embodiment of the present invention relates to an OLED, whichemits light with CIEx and CIEy color coordinates close to the CIEx(=0.131) and CIEy (=0.046) color coordinates of the primary color blue(CIEx=0.131 and CIEy=0.046) as defined by ITU-R Recommendation BT.2020(Rec. 2020) and thus is suited for the use in Ultra High Definition(UHD) displays, e.g. UHD-TVs. In commercial applications, typicallytop-emitting (top-electrode is transparent) devices are used, whereastest devices as used throughout the present application representbottom-emitting devices (bottom-electrode and substrate aretransparent). The CIEy color coordinate of a blue device can be reducedby up to a factor of two, when changing from a bottom- to a top-emittingdevice, while the CIEx remains nearly unchanged (Okinaka et al.doi:10.1002/sdtp.10480). Accordingly, a further embodiment of thepresent invention relates to an OLED, whose emission exhibits a CIExcolor coordinate of between 0.02 and 0.30, preferably between 0.03 and0.25, more preferably between 0.05 and 0.20 or even more preferablybetween 0.08 and 0.18 or even between 0.10 and 0.15 and/or a CIEy colorcoordinate of between 0.00 and 0.45, preferably between 0.01 and 0.30,more preferably between 0.02 and 0.20 or even more preferably between0.03 and 0.15 or even between 0.04 and 0.10.

A further embodiment of the present invention relates to an OLED, whichemits light with CIEx and CIEy color coordinates close to the CIEx(=0.170) and CIEy (=0.797) color coordinates of the primary color green(CIEx=0.170 and CIEy=0.797) as defined by ITU-R Recommendation BT.2020(Rec. 2020) and thus is suited for the use in Ultra High Definition(UHD) displays, e.g. UHD-TVs. In this context, the term “close to”refers to the ranges of CIEx and CIEy coordinates provided at the end ofthis paragraph. In commercial applications, typically top-emitting(top-electrode is transparent) devices are used, whereas test devices asused throughout the present application represent bottom-emittingdevices (bottom-electrode and substrate are transparent). The CIEy colorcoordinate of a blue device can be reduced by up to a factor of two,when changing from a bottom- to a top-emitting device, while the CIExremains nearly unchanged (Okinaka et al. doi:10.1002/sdtp.10480).Accordingly, a further embodiment of the present invention relates to anOLED, whose emission exhibits a CIEx color coordinate of between 0.06and 0.34, preferably between 0.07 and 0.29, more preferably between 0.09and 0.24 or even more preferably between 0.12 and 0.22 or even between0.14 and 0.19 and/or a CIEy color coordinate of between 0.75 and 1.20,preferably between 0.76 and 1.05, more preferably between 0.77 and 0.95or even more preferably between 0.78 and 0.90 or even between 0.79 and0.85.

A further embodiment of the present invention relates to an OLED, whichemits light with CIEx and CIEy color coordinates close to the CIEx(=0.708) and CIEy (=0.292) color coordinates of the primary color red(CIEx=0.708 and CIEy=0.292) as defined by ITU-R Recommendation BT.2020(Rec. 2020) and thus is suited for the use in Ultra High Definition(UHD) displays, e.g. UHD-TVs. In this context, the term “close to”refers to the ranges of CIEx and CIEy coordinates provided at the end ofthis paragraph. In commercial applications, typically top-emitting(top-electrode is transparent) devices are used, whereas test devices asused throughout the present application represent bottom-emittingdevices (bottom-electrode and substrate are transparent). The CIEy colorcoordinate of a blue device can be reduced by up to a factor of two,when changing from a bottom- to a top-emitting device, while the CIExremains nearly unchanged (Okinaka et al. doi:10.1002/sdtp.10480).Accordingly, a further embodiment of the present invention relates to anOLED, whose emission exhibits a CIEx color coordinate of between 0.60and 0.88, preferably between 0.61 and 0.83, more preferably between 0.63and 0.78 or even more preferably between 0.66 and 0.76 or even between0.68 and 0.73 and/or a CIEy color coordinate of between 0.25 and 0.70,preferably between 0.26 and 0.55, more preferably between 0.27 and 0.45or even more preferably between 0.28 and 0.40 or even between 0.29 and0.35.

As used throughout the present application, the terms “aryl” and“aromatic” may be understood in the broadest sense as any mono-, bi- orpolycyclic aromatic moieties. If not otherwise indicated, an aryl mayalso be optionally substituted by one or more substituents which areexemplified further throughout the present application. For example, anaryl may be a phenyl, naphthalene or anthracene. In a preferredembodiment, an aryl residue is a phenyl residue. If not otherwise 5indicated, an aryl may also be optionally substituted by one or moresubstituents which are exemplified further throughout the presentapplication. Accordingly, the term “arylene” refers to a divalentresidue that bears two binding sites to other molecular structures andthereby serving as a linker structure.

As used throughout the present application, the terms “heteroaryl” and“heteroaromatic” may be understood in the broadest sense as any mono-,bi- or polycyclic heteroaromatic moieties that include at least oneheteroatom, in particular which bear from one to three heteroatoms peraromatic ring.

Exemplarily, a heteroaromatic residue may be selected from the groupconsisting of carbazol, triazine (e.g., 1,3,5-triazine),dibezothiophene, dibenzofurane, pyrrole, furan, thiophene, imidazole,oxazole, thiazole, triazole, pyrazole, pyridine, pyrazine andpyrimidine, and the like. In a preferred embodiment, heteroaromaticresidue is carbazol or 1,3,5-triazine. If not otherwise indicated, aheteroaryl may also be optionally substituted by one or moresubstituents which are exemplified further throughout the presentapplication. Accordingly, the term “heteroarylene” refers to a divalentresidue that bears two binding sites to other molecular structures andthereby serving as a linker structure.

As used throughout the present application, the term “alkyl” may beunderstood in the broadest sense as both, linear or branched chain alkylresidue. Preferred alkyl residues are those containing from one tofifteen carbon atoms (C₁-C₁₅-alkyl). Exemplarily, an alkyl residue maybe methyl, ethyl, propyl, isopropyl, butyl, isobutyl, tert-butyl, andthe like. If not otherwise indicated, an alkyl may also be optionallysubstituted by one or more substituents which are exemplified furtherthroughout the present application. Accordingly, the term “alkylene”refers to a divalent residue that bears two binding sites to othermolecular structures and thereby serving as a linker structure.

If not otherwise indicated, as used herein, in particular in the contextof aryl, arylene, heteroaryl, alkyl and the like, the term “substituted”may be understood in the broadest sense. Preferably, such substitutionmeans a residue selected from the group consisting of C₁-C₂₀-alkyl,C₇-C₁₉-alkaryl, and C₆-C₁₈-aryl. Accordingly, preferably, no chargedmoiety, more preferably no functional group is present in suchsubstitution.

It will be noticed that hydrogen can, at each occurrence, be replaced bydeuterium.

Unless otherwise specified, any of the layers of the various embodimentsmay be deposited by any suitable method. The layers in the context ofthe present invention, including the light-emitting layer B, mayoptionally be prepared by means of liquid processing (also designated as“film processing”, “fluid processing”, “solution processing” or “solventprocessing”). This means that the components comprised in the respectivelayer are applied to the surface of a part of a device in liquid state.Preferably, the layers in the context of the present invention,including the light-emitting layer B, may be prepared by means ofspin-coating. This method well-known to those skilled in the art allowsobtaining thin and (essentially) homogeneous layers.

Alternatively, the layers in the context of the present invention,including the light-emitting layer B, may be prepared by other methodsbased on liquid processing such as, e.g., casting (e.g., drop-casting)and rolling methods, and printing methods (e.g., inkjet printing,gravure printing, blade coating). This may optionally be carried out inan inert atmosphere (e.g., in a nitrogen atmosphere).

In another preferred embodiment, the layers in the context of thepresent invention may be prepared by any other method known in the art,including but not limited to vacuum processing methods well-known tothose skilled in the art such as, e.g., thermal (co-)evaporation,organic vapor phase deposition (OVPD), and deposition by organic vaporjet printing (OVJP).

When preparing layers by means of liquid processing, the solutionsincluding the components of the layers (i.e., with respect to thelight-emitting layer B of the present invention, at least one hostcompound H^(B) and, typically, at least one TADF material E^(B), atleast one depopulation agent S^(B) (which is exemplarily a second TADFmaterial S^(B)) and optionally one or more other host compounds H^(B2))may further comprise a volatile organic solvent. Such volatile organicsolvent may optionally be one selected from the group consisting oftetrahydrofuran, dioxane, chlorobenzene, diethylene glycol diethylether, 2-(2-ethoxyethoxy)ethanol, gamma-butyrolactone, N-methylpyrrolidinon, ethoxyethanol, xylene, toluene, anisole, phenetol,acetonitrile, tetrahydrothiophene, benzonitrile, pyridine,trihydrofuran, triarylamine, cyclohexanone, acetone, propylenecarbonate, ethyl acetate, benzene and PGMEA (propylen glycol monoethylether acetate). Also a combination of two or more solvents may be used.After applied in liquid state, the layer may subsequently be driedand/or hardened by any means of the art, exemplarily at ambientconditions, at increased temperature (e.g., about 50° C. or about 60°C.) or at diminished pressure.

Optionally, an organic electroluminescent device (e.g., an OLED) mayexemplarily be an essentially white organic electroluminescent device ora blue organic electroluminescent device. Exemplarily such white organicelectroluminescent device may comprise at least one (deep) blue emittercompound (e.g., TADF material E^(B)) and one or more emitter compoundsemitting green and/or red light. Then, there may also optionally beenergy transmittance between two or more compounds as described above.

The organic electroluminescent device as a whole may also form a thinlayer of a thickness of not more than 5 mm, more than 2 mm, more than 1mm, more than 0.5 mm, more than 0.25 mm, more than 100 μm, or more than10 μm.

An organic electroluminescent device (e.g., an OLED) may be asmall-sized (e.g., having a surface not larger than 5 mm², or even notlarger than 1 mm²), medium-sized (e.g., having a surface in the range of0.5 to 20 cm²), or a large-sized (e.g., having a surface larger than 20cm²). An organic electroluminescent device (e.g., an OLED) according tothe present invention may optionally be used for generating screens, aslarge-area illuminating device, as luminescent wallpaper, luminescentwindow frame or glass, luminescent label, luminescent poser or flexiblescreen or display. Next to the common uses, an organicelectroluminescent device (e.g., an OLED) may exemplarily also be usedas luminescent films, “smart packaging” labels, or innovative designelements. Further they are usable for cell detection and examination(e.g., as bio labelling).

One of the main purposes of an organic electroluminescent device is thegeneration of light. Thus, the present invention further relates to amethod for generating light of a desired wavelength range, comprisingthe step of providing an organic electroluminescent device according toany the present invention.

Accordingly, a further aspect of the present invention relates to amethod for generating light of a desired wavelength range, comprisingthe steps of

-   (i) providing an organic electroluminescent device according to the    present invention; and-   (ii) applying an electrical current to said organic    electroluminescent device.

A further aspect of the present invention relates to a process of makingthe organic electroluminescent devices by assembling the elementsdescribed above. The present invention also relates to a method forgenerating blue, green, yellow, orange, red or white light, inparticular blue or white light by using said organic electroluminescentdevice. The invention is illustrated by the examples and claims.

EXAMPLES Cyclic Voltammetry

Cyclic voltammograms of solutions having concentration of 10-3 mol/l ofthe organic molecules in dichloromethane or a suitable solvent and asuitable supporting electrolyte (e.g. 0.1 mol/l of tetrabutylammoniumhexafluorophosphate) are measured. The measurements are conducted atroom temperature and under nitrogen atmosphere with a three-electrodeassembly (Working and counter electrodes: Pt wire, reference electrode:Pt wire) and calibrated using FeCp₂/FeCp₂ ⁺ as internal standard. HOMOdata was corrected using ferrocene as internal standard against SCE.

Density Functional Theory Calculation

Molecular structures are optimized employing the BP86 functional and theresolution of identity approach (RI). Excitation energies are calculatedusing the (BP86) optimized structures employing Time-Dependent DFT(TD-DFT) methods. Orbital and excited state energies are calculated withthe B3LYP functional. Def2-SVP basis sets (and a m4-grid for numericalintegration were used. The Turbomole program package was used for allcalculations.

Photophysical Measurements

Sample Preparation of host material and organic TADF emitters:

Stock solution 1: 10 mg of sample (organic TADF material or hostmaterial) is dissolved in 1 ml of solvent.Stock solution 2: 10 mg of PMMA is dissolved in 1 ml solvent.

The solvent is typically selected from toluene, chlorobenzene,dichloromethane and chloroform.

An Eppendorf pipette is used to add 1 ml of stock solution 1 to 9 ml ofstock solution 2 to achieve a 10% by weight of sample in PMMA.

Alternatively, the photophysical properties of host material can becharacterized in neat films of host material.

Sample Preparation of fluorescence emitters and NRCT emitters:

Stock solution 1: 10 mg of sample (fluorescence emitters and NRCTemitters) is dissolved in 1 ml of solvent.Stock solution 1a: 9 ml of solvent is added to 1 ml of stock solution 1.Stock solution 2: 10 mg of PMMA is dissolved in 1 ml solvent.

The solvent is typically selected from toluene, chlorobenzene,dichloromethane and chloroform.

An Eppendorf pipette is used to add 1 ml of stock solution 1 to 9.9 mlof stock solution 2 to achieve a 1% by weight of sample in PMMA.

Alternatively, the photophysical properties of fluorescence emitters canbe characterized in solution, wherein a concentration of 0.001 mg/ml offluorescence emitter in solution is used.

Sample Pretreatment: Spin-Coating

Apparatus: Spin150, SPS euro.Program: 1) 3 s at 400 U/min; 20 s at 1000 U/min at 1000 Upm/s. 3) 10 sat 4000 U/min at 1000 Upm/s. After coating, the films are dried at 70°C. for 1 min.

Photoluminescence Spectroscopy and TCSPC (Time-Correlated Single-PhotonCounting)

Steady-state emission spectroscopy is recorded using a HoribaScientific, Modell FluoroMax-4 equipped with a 150 W Xenon-Arc lamp,excitation- and emissions monochromators and a Hamamatsu R928photomultiplier and a time-correlated single-photon counting option.Emissions and excitation spectra are corrected using standard correctionfits.

Excited state lifetimes are determined employing the same system usingthe TCSPC method with FM-2013 equipment and a Horiba Yvon TCSPC hub.

Excitation Sources:

NanoLED 370 (wavelength: 371 nm, puls duration: 1.1 ns)NanoLED 290 (wavelength: 294 nm, puls duration: <1 ns)SpectraLED 310 (wavelength: 314 nm)SpectraLED 355 (wavelength: 355 nm).

Data analysis (exponential fit) was done using the software suiteDataStation and DAS6 analysis software. The fit is specified using thechi-squared-test.

Photoluminescence Quantum Yield Measurements

For photoluminescence quantum yield (PLQY) measurements an Absolute PLQuantum Yield Measurement C9920-03G system (Hamamatsu Photonics) isused. Quantum yields and CIE coordinates were determined using thesoftware U6039-05 version 3.6.0.

Emission maxima are given in nm, quantum yields CD in % and CIEcoordinates as x,y values.

PLQY was determined using the following protocol:

-   -   1) Quality assurance: Anthracene in ethanol (known        concentration) is used as reference    -   2) Excitation wavelength: the absorption maximum of the organic        molecule is determined and the molecule is excited using this        wavelength    -   3) Measurement        -   Quantum yields are measured for sample of solutions or films            under nitrogen atmosphere. The yield is calculated using the            equation:

$\Phi_{PL} = {\frac{n_{photon},{emited}}{n_{photon},{absorbed}} = \frac{\int{{\frac{\lambda}{hc}\left\lbrack {{{Int}_{emitted}^{sample}(\lambda)} - {{Int}_{absorbed}^{sample}(\lambda)}} \right\rbrack}d\lambda}}{\int{{\frac{\lambda}{hc}\left\lbrack {{{Int}_{emitted}^{reference}(\lambda)} - {{Int}_{absorbed}^{reference}(\lambda)}} \right\rbrack}d\lambda}}}$

-   -   wherein n_(photon) denotes the photon count and Int. is the        intensity.

Production and Characterization of Organic Electroluminescence Devices

Via vacuum-deposition methods OLED devices comprising organic moleculesaccording to the invention can be produced. If a layer contains morethan one compound, the weight-percentage of one or more compounds isgiven in %. The total weight-percentage values amount to 100%, thus if avalue is not given, the fraction of this compound equals to thedifference between the given values and 100%.

The not fully optimized OLEDs are characterized using standard methodsand measuring electroluminescence spectra, the external quantumefficiency (in %) in dependency on the intensity, calculated using thelight detected by the photodiode, and the current. The OLED devicelifetime is extracted from the change of the luminance during operationat constant current density, which is given in mA/cm². The LT50 valuecorresponds to the time, where the measured luminance decreased to 50%of the initial luminance, analogously LT80 corresponds to the timepoint, at which the measured luminance decreased to 80% of the initialluminance, LT97 to the time point, at which the measured luminancedecreased to 97% of the initial luminance etc.

Accelerated lifetime measurements are performed (e.g. applying increasedcurrent densities). Exemplarily LT95 values at 1200 cd/m² are determinedusing the following equation:

${LT95\left( {1200\frac{cd}{m^{2}}} \right)} = {LT95\left( L_{0} \right)\left( \frac{L_{0}}{1200\frac{cd}{m^{2}}} \right)^{1.6}}$

wherein L₀ denotes the initial luminance at the applied current density.

The values correspond to the average of several pixels (typically two toeight), the standard deviation between these pixels is given. Theresults show the data series for one OLED pixel.

Comparative Examples C1 and Examples E1 to E7

Depopulation Agent 7

TABLE 1 Physicochemical properties of the materials Material E^(HOMO)[eV] E^(LUMO) [eV] S1 [eV] T1 [eV] mCBP (H^(B)) −6.02 −2.42 3.60 2.82TADF1 (E^(B)) −5.99 −3.35 2.64 2.65 Depopulation Agent 1 −5.48 −2.732.75 2.59 (S^(B)) Depopulation Agent 2 −5.54 −2.20 3.34 2.9 (S^(B))Depopulation Agent 3 −5.55 −2.69 2.86 (S^(B)) Depopulation Agent 4 −5.72−2.95 2.77 2.60 (S^(B)) Depopulation Agent 5 −5.66 −2.35 3.31 2.71(S^(B)) Depopulation Agent 6 −5.66 −2.70 2.96 (S^(B)) Depopulation Agent7 −5.86 −2.88 2.98 2.62 (S^(B))

TABLE 2 Examples of setups of devices D1 to D7 Comparative LayerThickness Examples (Ex.) Example C1 10 100 nm Al Al  9  2 nm Liq Liq  8 20 nm NBPhen NBPhen  7  10 nm HBL1 HBL1  6  50 nm Depopulation Agentselected from TADF1 (20%): light- Depopulation Agents 1 to 7 (each mCBP(80%) emitting 1% by weight or 5% by weight): layer B TADF1 (20% byweight): add up to a total of 100% by weight, based on thelight-emitting layer B of mCBP (i.e., 79% by weight or 75% by weight,respectively)  5  10 nm mCBP mCBP  4  10 nm TCTA TCTA  3  50 nm NPB NPB 2  5 nm HAT-CN HAT-CN  1  50 nm ITO ITO substrate glass glass

TABLE 3 Photophysical properties of layers Concen- Relative tration ofRelative LT95 at Device No. depopulation E^(HOMO)(S^(B))- EQE at 1200 ΔλEx. (depopulation agent [% E^(HOMO)(H^(B)) 1000 cd/m² max No. agent) byweight] [eV] cd/m² [h] [nm] C1 C1 0 0 1 1 0 (No Depopulation Agent) E1aD1 1 0.54 1.15 3.39 3 E1b (Depopulation 5 0.54 1.01 1.41 12  Agent 1)E2a D2 1 0.48 1.08 2.64 2 E2b (Depopulation 5 0.48 1.12 2.35 2 Agent 2)E3a D3 1 0.47 0.99 4.04 2 E3b (Depopulation 5 0.47 0.98 2.11 2 Agent 3)E4a D4 1 0.3 1.01 1.99 2 E4b (Depopulation 5 0.3 1.03 1.83 2 Agent 4)E5a D5 1 0.36 1.04 2.5 2 E5b (Depopulation 5 0.36 1.06 4.2 2 Agent 5)E6a D6 1 0.36 1 1.45 2 E6b (Depopulation 5 0.36 1.02 1.33 2 Agent 6) E7aD7 1 0.16 1.01 1.04 0 E7b (Depopulation 5 0.16 1.02 1.04 0 Agent 7) Δλmax (nm) denotes the difference in the emission maximum λ _(max) (nm) ofthe comparative device C1 (λ _(max) (nm)^(comp)) and the example (λ_(max) (nm)^(exp)): Δλ _(max) (nm) = λ _(max) (nm)^(comp) − λ _(max)(nM)^(exp).

The emitting layer of Comparative device C1 only contains TADF1 and mCBPThe external quantum efficiency (FOE) at 1000 cd/m² is 16% and thelifetime LT95 at 1200 cd/m² value was determined to be 490 h. Theemission maximum is at 520 nm at 10 mA/cm². The corresponding CIFx valueis 0.306 and CIFy is 0.604.

Device D1 comprises the same layer arrangement as device D1, except thatthe emitting layer contains TADF1, mCBP and Depopulation Agent 1 witheither 1% by weight or 5% by weight. The concentration by weight ofTADF1 is always set to 20% by weight, wherein the concentration of mCBPis either 79% by weight, in case the Depopulation Agent is used with 1%by weight or 75% by weight, in case the Depopulation Agent is used with5% by weight.Device D2 is prepared in the same manner as device D1, unless changingthe Depopulation Agent 1 to Depopulation Agent 2.Device D3 is prepared in the same manner as device D1, unless changingthe Depopulation Agent 1 to Depopulation Agent 3.Device D4 is prepared in the same manner as device D1, unless changingthe Depopulation Agent 1 to Depopulation Agent 4.Device D5 is prepared in the same manner as device D1, unless changingthe Depopulation Agent 1 to Depopulation Agent 5.Device D6 is prepared in the same manner as device D1, unless changingthe Depopulation Agent 1 to Depopulation Agent 6.Device D7 is prepared in the same manner as device D1, unless changingthe Depopulation Agent 1 to Depopulation Agent 7.

It was surprisingly found that the presence of a depopulation agent maylead to an increasing lifetime in a device according to the presentinvention, while the EQE is at least similar, often increased. Theemitted color/emission maximum wavelength typically remains in an atleast similar range. For all devices with a Depopulation Agent, whichshows a E^(HOMO)(S^(B))−E^(HOMO)(H^(B))>0.2 eV a significant enhancedLT95 at 1200 cd/m² can be observed compared to the comparative exampleC1 without a Depopulation Agent and compared to example D7, as therelative lifetime LT95 at 1200 cd/m² is enhanced by at least 30% and upto more than 300%.

1-16. (canceled)
 17. An organic electroluminescent device comprising alight-emitting layer B comprising: (i) a host material H^(B), which hasa lowermost excited singlet state energy level S1^(H), a lowermostexcited triplet state energy level T1^(H), and a highest occupiedmolecular orbital HOMO(H^(B)) having an energy E^(HOMO)(H^(B)); (ii) athermally activated delayed fluorescence (TADF) material E^(B), whichhas a lowermost excited singlet state energy level S1^(E), a lowermostexcited triplet state energy level T1^(E), and a highest occupiedmolecular orbital HOMO(E^(B)) having an energy E^(HOMO)(E^(B)); and(iii) a depopulation agent S^(B), which has a lowermost excited singletstate energy level S1^(S), optionally a lowermost excited triplet stateenergy level T1^(S), and a highest occupied molecular orbitalHOMO(S^(B)) having an energy E^(HOMO)(S^(B)); wherein E^(B) emitsthermally activated delayed fluorescence; and wherein the relationsexpressed by the following formulas (1) to (3) and either (4a) and (4b),or (5a) and (5b) apply:S1^(H) >S1^(E)  (1)S1^(H) >S1^(S)  (2)S1^(S) >S1^(E)  (3)E ^(HOMO)(E ^(B))≤E ^(HOMO)(H ^(B))  (4a)0.2 eV≤E ^(HOMO)(S ^(B))−E ^(HOMO)(E ^(B))≤0.8 eV  (4b)E ^(HOMO)(H ^(B))≥E ^(HOMO)(E ^(B))  (5a)0.2 eV≤E ^(HOMO)(S ^(B))−E ^(HOMO)(H ^(B))≤0.8 eV  (5b).
 18. The organicelectroluminescent device according to claim 17, wherein the TADFmaterial E^(B) has a ΔE_(ST) value, which corresponds to the energydifference between S1^(E) and T1^(E), of less than 0.4 eV.
 19. Theorganic electroluminescent device according to claim 17, wherein themass ratio of the TADF material E^(B) to depopulation agent S^(B)(E^(B):S^(B)) is >1.
 20. The organic electroluminescent device accordingto claim 17, wherein the organic electroluminescent device is selectedfrom the group consisting of an organic light emitting diode, a lightemitting electrochemical cell, and a light-emitting transistor.
 21. Theorganic electroluminescent device according to claim 17, wherein theTADF material E^(B) is an organic TADF emitter or a combination of twoor more organic TADF emitters.
 22. The organic electroluminescent deviceaccording to claim 17, wherein the depopulation agent S^(B) is anorganic TADF emitter or a combination of two or more organic TADFemitters.
 23. The organic electroluminescent device according to claim17, wherein the relation between the lowest unoccupied molecular orbitalLUMO(E^(B)) of the TADF material E^(B) having an energy E_(LUMO)(E^(B))and the lowest unoccupied molecular orbital LUMO(S^(B)) of thedepopulation agent S^(B) having an energy E^(LUMO)(S^(B)) expressed byformula (7) applies:E ^(LUMO)(S ^(B))>E ^(LUMO)(E ^(B))  (7).
 24. The organicelectroluminescent device according to claim 17, wherein a relationexpressed by formula (6a), (6b), or (6c) applies:E ^(HOMO)(E ^(B))>E ^(HOMO)(H ^(B))  (6a)E ^(HOMO)(H ^(B))>E ^(HOMO)(E ^(B))  (6b)−0.2 eV≤E ^(HOMO)(H ^(B))−E ^(HOMO)(E ^(B))≤0.2 eV  (6c).
 25. Theorganic electroluminescent device according to claim 17, wherein thelight-emitting layer B comprises: (i) 39.8-98% by weight of the hostcompound H^(B); (ii) 0.1-50% by weight of the TADF material E^(B); and(iii) 0.1-50% by weight of depopulation agent S^(B); and optionally (iv)0-60% by weight of one or more further host compounds H^(B2) differingfrom H^(B); and optionally (v) 0-60% by weight of one or more solvents;and optionally (vi) 0-30% by weight of at least one further emittermolecule F.
 26. The organic electroluminescent device according to claim17, wherein the light-emitting layer B comprises 1-8% by weight of thedepopulation agent S^(B).
 27. The organic electroluminescent deviceaccording to claim 17, wherein the depopulation agent S^(B) has aΔE_(ST) value, which corresponds to the energy difference between S1^(S)and T1^(S), of less than 0.4 eV.
 28. The organic electroluminescentdevice according to claim 17, wherein the TADF emitter E^(B) and/or thedepopulation agent S^(B) comprises or consists of a structure accordingto Formula I-TADF

wherein: is at each occurrence independently from another 1 or 2; p isat each occurrence independently from another 1 or 2; X is at eachoccurrence independently from another selected from the group consistingof Ar^(EWG)H, CN, and CF₃; Z is at each occurrence independently fromanother selected from the group consisting of a direct bond, CR³R⁴,C═CR³R⁴, C═O, C═NR³, NR³, O, SiR³R⁴, S, S(O), and S(O)₂; Ar^(EWG) is ateach occurrence independently from another a structure according to oneof Formulas IIa to IIk

wherein # represents the binding site of the single bond linkingAr^(EWG) to the substituted central phenyl ring of Formula I-TADF; R¹ isat each occurrence independently from another selected from the groupconsisting of hydrogen, deuterium, C₁-C₅-alkyl, wherein one or morehydrogen atoms are optionally substituted by deuterium, and C₆-C₁₈-aryl,which is optionally substituted with one or more substituents R⁶; R² isat each occurrence independently from another selected from the groupconsisting of hydrogen, deuterium, C₁-C₅-alkyl, wherein one or morehydrogen atoms are optionally substituted by deuterium, and C₆-C₁₈-aryl,which is optionally substituted with one or more substituents R⁶; R^(a),R³, and R⁴ are at each occurrence independently from another selectedfrom the group consisting of hydrogen, deuterium, N(R⁵)₂, OR⁵, SR₅,Si(R⁵)₃, CF₃, CN, F, C₁-C₄₀-alkyl, which is optionally substituted withone or more substituents R⁵ and wherein one or more non-adjacentCH₂-groups are optionally substituted by R⁵C═CR⁵, C≡C, Si(R⁵)₂, Ge(R⁵)₂,Sn(R⁵)₂, C═O, C═S, C═Se, C═NR⁵, P(═O)(R⁵), SO, SO₂, NR⁵, O, S, or CONR⁵;C₁-C₄₀-thioalkoxy, which is optionally substituted with one or moresubstituents R⁵ and wherein one or more non-adjacent CH₂-groups areoptionally substituted by R⁵C═CR⁵, C≡C, Si(R⁵)₂, Ge(R⁵)₂, Sn(R⁵)₂, C═O,C═S, C═Se, C═NR⁵, P(═O)(R⁵), SO, SO₂, NR⁵, O, S, or CONR⁵; C₆-C₆₀-aryl,which is optionally substituted with one or more substituents R⁵; andC₃-C₅₇-heteroaryl, which is optionally substituted with one or moresubstituents R⁵; R⁵ is at each occurrence independently from anotherselected from the group consisting of hydrogen, deuterium, N(R⁶)₂, OR⁶,SR⁶, Si(R⁶)₃, CF₃, CN, F, C₁-C₄₀-alkyl, which is optionally substitutedwith one or more substituents R⁶ and wherein one or more non-adjacentCH₂-groups are optionally substituted by R⁶C═CR⁶, C≡C, Si(R⁶)₂, Ge(R⁶)₂,Sn(R⁶)₂, C═O, C═S, C═Se, C═NR⁶, P(═O)(R⁶), SO, SO₂, NR⁶, O, S, or CONR⁶;C₆-C₆₀-aryl, which is optionally substituted with one or moresubstituents R⁶; and C₃-C₅₇-heteroaryl, which is optionally substitutedwith one or more substituents R⁶; R⁶ is at each occurrence independentlyfrom another selected from the group consisting of hydrogen, deuterium,OPh, CF₃, CN, F, C₁-C₅-alkyl, wherein one or more hydrogen atoms areoptionally, independently from each other substituted by deuterium, CN,CF₃, or F; C₁-C₅-alkoxy, wherein one or more hydrogen atoms areoptionally, independently from each other substituted by deuterium, CN,CF₃, or F; C₁-C₅-thioalkoxy, wherein one or more hydrogen atoms areoptionally, independently from each other substituted by deuterium, CN,CF₃, or F; C₆-C₁₈-aryl, which is optionally substituted with one or moreC₁-C₅-alkyl substituents; C₃-C₁₇-heteroaryl, which is optionallysubstituted with one or more C₆-C₁₈-aryl substituents and/or one or moreC₁-C₅-alkyl substituents; N(C₆-C₁₈-aryl)₂; N(C₃-C₁₇-heteroaryl)₂; andN(C₃-C₁₇-heteroaryl)(C₆-C₁₈-aryl); R^(d) is at each occurrenceindependently from another selected from the group consisting ofhydrogen, deuterium, N(R⁵)₂, OR⁵, SR⁵, Si(R⁵)₃, CF₃, CN, F,C₁-C₄₀-alkyl, which is optionally substituted with one or moresubstituents R⁵ and wherein one or more non-adjacent CH₂-groups areoptionally substituted by R⁵C═CR⁵, C≡C, Si(R⁵)₂, Ge(R⁵)₂, Sn(R⁵)₂, C═O,C═S, C═Se, C═NR⁵, P(═O)(R⁵), SO, SO₂, NR⁵, O, S, or CONR⁵;C₁-C₄₀-thioalkoxy, which is optionally substituted with one or moresubstituents R⁵ and wherein one or more non-adjacent CH₂-groups areoptionally substituted by R⁵C═CR⁵, C≡C, Si(R⁵)₂, Ge(R⁵)₂, Sn(R⁵)₂, C═O,C═S, C═Se, C═NR⁵, P(═O)(R⁵), SO, SO₂, NR⁵, O, S, or CONR⁵; C₆-C₆₀-aryl,which is optionally substituted with one or more substituents R⁵; andC₃-C₅₇-heteroaryl which is optionally substituted with one or moresubstituents R⁵; wherein the substituents R^(a), R³, R⁴, or R⁵independently from each other may optionally form a mono- or polycyclic,aliphatic, aromatic, and/or benzo-fused ring system with one or moreother substituents R^(a), R³, R⁴, or R⁵; and wherein the one or moresubstituents R^(d) independently from each other may optionally form amono- or polycyclic, aliphatic, aromatic, and/or benzo-fused ring systemwith one or more other substituents R^(d).
 29. The organicelectroluminescent device according to claim 17, wherein depopulationagent S^(B) comprises or consists of a structure according to FormulaI-NRCT:

wherein: o is 0 or 1; m=1−o; X¹ is N or B; X² is N or B; X³ is N or B; Wis selected from the group consisting of Si(R^(3S))₂, C(R^(3S))₂, andBR^(3S); each of R^(1S), R^(2S), and R^(3S) is independently from eachother selected from the group consisting of: C₁-C₅-alkyl, which isoptionally substituted with one or more substituents R^(6S);C₆-C₆₀-aryl, which is optionally substituted with one or moresubstituents R^(6S); and C₃-C₅₇-heteroaryl, which is optionallysubstituted with one or more substituents R^(6S); each of R^(I), R^(II),R^(III), R^(IV), R^(V), R^(VI), R^(VII), R^(VIII), R^(IX), R^(X), andR^(XI) is independently from another selected from the group consistingof: hydrogen, deuterium, N(R^(5S))₂, OR^(5S), Si(R^(5S))₃, B(OR^(5S))₂,OSO₂R^(5S), CF₃, CN, halogen, C₁-C₄₀-alkyl, which is optionallysubstituted with one or more substituents R^(5S), and wherein one ormore non-adjacent CH₂-groups are each optionally substituted byR⁵⁵C═CR^(5S), C≡C, Si(R^(5S))₂, Ge(R^(5S))₂, Sn(R^(5S))₂, C═O, C═S,C═Se, C═NR^(5S), P(═O)(R^(5S)), SO, SO₂, NR^(5S), O, S, or CONR^(5S);C₁-C₄₀-alkoxy, which is optionally substituted with one or moresubstituents R^(5S), and wherein one or more non-adjacent CH₂-groups areeach optionally substituted by R^(5S)C═CR^(5S), C≡C, Si(R^(5S))₂,Ge(R^(5S))₂, Sn(R^(5S))₂, C═O, C═S, C═Se, C═NR^(5S), P(═O)(R^(5S)), SO,SO₂, NR^(5S), O, S, or CONR^(5S); C₁-C₄₀-thioalkoxy, which is optionallysubstituted with one or more substituents R^(5S), and wherein one ormore non-adjacent CH₂-groups are each optionally substituted byR^(5S)C═CR^(5S), C≡C, Si(R^(5S))₂, Ge(R^(5S))₂, Sn(R^(5S))₂, C═O, C═S,C═Se, C═NR^(5S), P(═O)(R^(5S)), SO, SO₂, NR^(5S), O, S, or CONR^(5S);C₂-C₄₀-alkenyl, which is optionally substituted with one or moresubstituents R^(5S), and wherein one or more non-adjacent CH₂-groups areeach optionally substituted by R^(5S)C═CR^(5S), C≡C, Si(R^(5S))₂,Ge(R^(5S))₂, Sn(R^(5S))₂, C═O, C═S, C═Se, C═NR^(5S), P(═O)(R^(5S)), SO,SO₂, NR^(5S), O, S, or CONR^(5S); C₂-C₄₀-alkynyl, which is optionallysubstituted with one or more substituents R^(5S), and wherein one ormore non-adjacent CH₂-groups are each optionally substituted byR^(5S)C═CR^(5S), C≡C, Si(R^(5S))₂, Ge(R^(5S))₂, Sn(R^(5S))₂, C═O, C═S,C═Se, C═NR^(5S), P(═O)(R^(5S)), SO, SO₂, NR⁵S, O, S, or CONR^(5S);C₆-C₆₀-aryl, which is optionally substituted with one or moresubstituents R^(5S); and C₃-C₅₇-heteroaryl, which is optionallysubstituted with one or more substituents RSS; R^(5S) is at eachoccurrence independently from another selected from the group consistingof: hydrogen, deuterium, OPh, CF₃, CN, F, C₁-C₅-alkyl, whereinoptionally one or more hydrogen atoms are independently from each othersubstituted by deuterium, CN, CF₃, or F; C₁-C₅-alkoxy, whereinoptionally one or more hydrogen atoms are independently from each othersubstituted by deuterium, CN, CF₃, or F; C₁-C₅-thioalkoxy, whereinoptionally one or more hydrogen atoms are independently from each othersubstituted by deuterium, CN, CF₃, or F; C₂-C₅-alkenyl, whereinoptionally one or more hydrogen atoms are independently from each othersubstituted by deuterium, CN, CF₃, or F; C₂-C₅-alkynyl, whereinoptionally one or more hydrogen atoms are independently from each othersubstituted by deuterium, CN, CF₃, or F; C₆-C₁₈-aryl, which isoptionally substituted with one or more C₁-C₅-alkyl substituents;C₃-C₁₇-heteroaryl, which is optionally substituted with one or moreC₁-C₅-alkyl substituents; N(C₆-C₁₈-aryl)₂; N(C₃-C₁₇-heteroaryl)₂; andN(C₃-C₁₇-heteroaryl)(C₆-C₁₈-aryl); R^(6S) is at each occurrenceindependently from another selected from the group consisting ofhydrogen, deuterium, OPh, CF₃, CN, F, C₁-C₅-alkyl, wherein optionallyone or more hydrogen atoms are independently from each other substitutedby deuterium, CN, CF₃, or F; C₁-C₅-alkoxy, wherein optionally one ormore hydrogen atoms are independently from each other substituted bydeuterium, CN, CF₃, or F; C₁-C₅-thioalkoxy, wherein optionally one ormore hydrogen atoms are independently from each other substituted bydeuterium, CN, CF₃, or F; C₂-C₅-alkenyl, wherein optionally one or morehydrogen atoms are independently from each other substituted bydeuterium, CN, CF₃, or F; C₂-C₅-alkynyl, wherein optionally one or morehydrogen atoms are independently from each other substituted bydeuterium, CN, CF₃, or F; C₆-C₁₈-aryl, which is optionally substitutedwith one or more C₁-C₅-alkyl substituents; C₃-C₁₇-heteroaryl, which isoptionally substituted with one or more C₁-C₅-alkyl substituents;N(C₆-C₁₅-aryl)₂; N(C₃-C₁₇-heteroaryl)₂; andN(C₃-C₁₇-heteroaryl)(C₆-C₁₅-aryl); wherein two or more of thesubstituents selected from the group consisting of R^(I), R^(II),R^(III), R^(IV), R^(V), R^(VI), R^(VII), R^(VIII), R^(IX), R^(X), andR^(XI) that are positioned adjacent to another may optionally each forma mono- or polycyclic, aliphatic, aromatic, and/or benzo-fused ringsystem with another; and wherein at least one of X¹, X², and X³ is B andat least one of X¹, X², and X³ is N.
 30. A method for generating visiblelight comprising the steps of: (i) providing an organicelectroluminescent device according to claim 17; and (ii) applying anelectrical current to the organic electroluminescent device.
 31. Athermally activated delayed fluorescence (TADF) material E^(B) incombination with at least one host material H^(B) and at least onedepopulation agent S^(B) in a light-emitting layer for increasing thelifetime of the organic electroluminescent device.
 32. The TADF materialE^(B) in combination with at least one host material H^(B) and at leastone depopulation agent S^(B) in a light-emitting layer of claim 31,wherein: (i) the host material H^(B) has a lowermost excited singletstate energy level S1^(H), a lowermost excited triplet state energylevel T1^(H), and a highest occupied molecular orbital HOMO(H^(B))having an energy E^(HOMO)(H^(B)); (ii) the TADF material E^(B) has alowermost excited singlet state energy level S1^(E), a lowermost excitedtriplet state energy level T1^(E), and a highest occupied molecularorbital HOMO(E^(B)) having an energy E^(HOMO)(E^(B)); and (iii) thedepopulation agent S^(B) has a lowermost excited singlet state energylevel S1^(S), optionally a lowermost excited triplet state energy levelT1^(S), and a highest occupied molecular orbital HOMO(S^(B)) having anenergy E^(HOMO)(S^(B)); wherein E^(B) emits thermally activated delayedfluorescence; and wherein the relations expressed by the followingformulas (1) to (3) and either (4a) and (4b), or (5a) and (5b) apply:S1^(H) >S1^(E)  (1)S1^(H) >S1^(S)  (2)S1^(S) >S1^(E)  (3)E ^(HOMO)(E ^(B))≤E ^(HOMO)(H ^(B))  (4a)0.2 eV≤E ^(HOMO)(S ^(B))−E ^(HOMO)(E ^(B))≤0.8 eV  (4b)E ^(HOMO)(H ^(B))≥E ^(HOMO)(E ^(B))  (5a)0.2 eV≤E ^(HOMO)(S ^(B))−E ^(HOMO)(H ^(B))≤0.8 eV  (5b).